Dan Halperin, Publications

robust geometric computing and CGAL
arrangements
robotics, algorithmic motion planning, assembly planning
molecular modeling
miscellaneous
surveys


Robust geometric computing and CGAL

E. Fogel, D. Halperin, L. Kettner, M. Teillaud, R. Wein and N. Wolpert
Arrangements
Effective Computational Geometry for Curves and Surfaces, Jean-Daniel Boissonnat and Monique Teillaud (eds.), Springer, Mathematics and Visualization series, 2007, Chapter 1, pp. 1-66.
[BibTex]

M. de Berg, D. Halperin and M. Overmars
An intersection-sensitive algorithm for snap rounding
Computational Geometry: Theory and Applications 36, 2007, pp. 159-165.
[BibTex]

E. Fogel and D. Halperin
Exact and Efficient Construction of Minkowski Sums of Convex Polyhedra with Applications
ALENEX 2006, Miami, Florida, 2006
[BibTex]

I. Haran and D. Halperin
An Experimental Study of Point Location in General Planar Arrangements
ALENEX 2006, Miami, Florida, 2006
[BibTex]

R. Wein, E. Fogel, B. Zukerman and D. Halperin
Advanced programming techniques applied to CGAL's arrangement package
Proc. Library-Centric Software Design Workshop, LCSD'05, San Diego, California, 2005
[BibTex]

E. Fogel and D. Halperin
Video: Exact Minkowski sums of convex polyhedra
Proc. 21st ACM Symposium on Computational Geometry, SoCG 2005, Pisa, Italy, 2005,  382-383.
[BibTex]

E. Fogel, R. Wein and D. Halperin
Code flexibility and program efficiency by genericity: Improving CGAL's arrangements
Proc. 12th Annual European Symposium on Algorithms (ESA), Bergen, Norway, 2004, 664-676.
[BibTex]

E. Fogel et al.
An empirical comparison of software for constructing arrangements of curved arcs (preliminary version)
ECG Technical Report No.: ECG-TR-361200-01, Tel Aviv University.
[BibTex]

D. Halperin and E. Leiserowitz
Controlled perturbation for arrangements of circles
International Journal of Computational Geometry and Applications, 14 (4 & 5), 2004, pp. 277-310. Special issue, papers from SoCG 2003..
A preliminary version appeared in Proc. 19th ACM Symposium on Computational Geometry, SoCG 2003, San Diego, 264-273.
[BibTex]

D. Halperin and E. Packer
Iterated snap rounding
Computational Geometry: Theory and Applications, 23(2), 2002, pp. 209-222.
A preliminary version appeared in Abstracts 17th European Workshop on Computational Geometry, Berlin, 2001,  82-85.
[BibTex]

D. Halperin
Robust geometric computing in motion
International Journal of Robotics Research, 21 (3), 2002, pp. 219-232.
Appeared in: Algorithmic and Computational Robotics: New Dimensions (WAFR '00). B.R. Donald and K.M. Lynch and D. Rus (eds.,) A.K. Peters, Wellesley, 2001, pp. 9-22.
(Invited talk at WAFR 2000, Workshop on Algorithmic Foundations of Robotics , Dartmouth College, March 2000).
[BibTex]

E. Ezra,  D. Halperin and M. Sharir
Speeding up the incremental construction of the union of geometric objects in practice.
Computational Geometry: Theory and Applications, 27 (2004), pp. 63-85. Special issue, papers from the 18th European Workshop on Computational Geometry, Warsaw, April 2002.
A preliminary version appeared in Proc. 10th Europen Symposium on Algorithms (ESA), Rome, 2002, 473-484.
[BibTex]

E. Flato, E. Fogel, D. Halperin and E. Leiserowitz
Video: Exact Minkowski sums and applications
Proc. 18th ACM Symposium on Computational Geometry, Barcelona, 2002,  273-274.
[BibTex]

P.K. Agarwal, E. Flato and D. Halperin
Polygon decomposition for efficient construction of Minkowski sums
Computational Geometry: Theory and Applications, Special Issue, selected papers from the European Workshop on Computational
Geometry, Eilat, 2000, vol. 21 (2002), 39-61.
A preliminary version appeared in Proc. 8th European Symposium on Algorithms (ESA), Saarbrücken, 2000. Springer LNCS Vol. 1879,  20-31.
See also Eyal Flato's thesis.
[BibTex]

E. Flato and D. Halperin
Robust and efficient construction of planar Minkowski sums
Abstracts 16th European Workshop on Computational Geometry, Eilat, 2000,  85-88.
See also Eyal Flato's thesis.
[BibTex]

I. Hanniel and D. Halperin
Two-dimensional arrangements in CGAL and adaptive point location for parametric curves
Proc. 4th International Workshop on Algorithm Engineering (WAE), Saarbrücken, LNCS Vol. 1982, Springer, 2000, 171-182.
See also Iddo Hanniel's thesis.
[BibTex]

E. Flato, D. Halperin, I. Hanniel, O. Nechushtan and E. Ezra
The design and implementation of planar maps in CGAL
The ACM Journal of Experimental Algorithmics Volume 5, 2000, pp. 1-23.
A preliminary version appeared in Proc. 3rd International Workshop on Algorithm Engineering (WAE), London, 1999, Springer LNCS Vol. 1668, 154-168
[BibTex]

C. Linhart, D. Halperin, S. Har-Peled and I. Hanniel,
On-line zone construction in arrangements of lines in the plane
International Journal of Computational Geometry and Applications, 13:6 (2003), pp. 463-485.
A preliminary version with Y. Aharoni appeared in Proc. 3rd International Workshop on Algorithm Engineering (WAE), London, 1999,
Springer LNCS Vol. 1668, 139-153.
[BibTex]

D. Halperin and C.R. Shelton
A perturbation scheme for spherical arrangements with application to molecular modeling (the full version, MIT AI MEMO)
Computational Geometry: Theory and Applications 10 (4), 1998, pp. 273-288.
A preliminary version appeared in Proc. 13th ACM  Symposium on Computational Geometry, Nice, 1997, 183-192.
[BibTex]

D. Halperin and S. Raab
Full version: Controlled perturbation for arrangements of polyhedral surfaces
A preliminary version entitled: Controlled perturbation for arrangements of polyhedral surfaces with application to swept volumes
by S. Raab appeared in Proc. 15th ACM Symposium on Computational Geometry, Miami, 1999, 163-172.
See also Sigal Raab's thesis.
[BibTex]
 



Arrangements

Papers reporting on the experimental study of arrangements including arrangements in CGAL appear above under robust geometric computing and CGAL

D. Halperin
Arrangements
CRC Handbook of Discrete and Computational Geometry, 2nd Edition, J.E. Goodman and J. O'Rourke (eds.), CRC Press, Inc., Boca Raton, FL, 2004, pp. 529-562.
[BibTex]

H. Shaul and D. Halperin
Improved construction of vertical decompositions of 3D arrangements
Proc. 18th ACM Symposium on Computational Geometry, Barcelona, 2002,  283-292.
[BibTex]

B. Aronov, A. Efrat, D. Halperin, and M. Sharir
On the number of regular vertices of the union of Jordan regions
Discrete and Computational Geometry, 25 (2001), 203-220.
A preliminary version appeared in Proc. 6th Scandinavian Workshop on Algorithm Theory (SWAT), Stockholm, 1998, pp. 322-334.
[BibTex]

M. de Berg, D. Halperin, M.H. Overmars and M. van Kreveld
Sparse arrangements and the number of views of polyhedral scenes
International Journal of Computational Geometry and Applications 7 (1997), 175-195.
[BibTex]

M. de Berg, L.J. Guibas and D. Halperin
Vertical decompositions for triangles in 3-space
Discrete and Computational Geometry, 15 (1996), 36--61
A preliminary version appeared in Proc. 10th ACM  Symposium on Computational Geometry, Stony Brook, 1994, 1-10.
[BibTex]

D. Halperin and M. Sharir
Almost tight upper bounds for the single cell and zone problems in three dimensions
Discrete and Computational Geometry, special issue of papers from the 10th ACM Symposium on Computational Geometry, 14 (1995), 385--410.
A preliminary version appeared in Proc. 10th ACM  Symposium on Computational Geometry, Stony Brook, 1994, 11-20.
[BibTex]

L.J. Guibas, D. Halperin, J. Matousek and M. Sharir
On vertical decomposition of arrangements of hyperplanes in four dimensions
Discrete and Computational Geometry 14 (1995), 113--122
A preliminary version appeared in Proc. 5th Canadian Conference on Computational Geometry, Waterloo, 1993, pp. 127-132.
[BibTex]

S. Har-Peled, T. M. Chan, B. Aronov, D. Halperin and J. Snoeyink
The complexity of a single face of a Minkowski sum
Proc. 7th Canadian Conference on Computational Geometry, University Laval, Quebec, 1995, pp. 91-96
[BibTex]

D. Halperin and M. Sharir
Arrangements and their applications in robotics: Recent developments
The Algorithmic Foundations of Robotics, K. Goldberg, D. Halperin, J.C. Latombe and R. Wilson, Eds., A.K. Peters, Boston, MA, 1995, 495--511.
A preliminary version appeared in Proc. 1st Workshop on the Algorithmic Foundations of Robotics, San Francisco, 1994.
[BibTex]

E.M. Arkin, D. Halperin, K. Kedem, J.S.B. Mitchell and N. Naor
Arrangements of segments that share endpoints: Single face results
Discrete and Computational Geometry 13 (1995), L\'aszl\'o Fejes T\'oth Festschrift, 257--270.
A preliminary version appeared in Proc. 7th ACM  Symposium on Computational Geometry, North Conway, 1991, pp. 324-333.
[BibTex]

D. Halperin and M. Sharir
New bounds for lower envelopes in three dimensions, with applications to visibility in terrains
Discrete and Computational Geometry 12 (1994), 313-326.
A preliminary version appeared in Proc. 9th ACM  Symposium on Computational Geometry, San Diego, 1993, 11-18.
[BibTex]

D. Halperin
On the complexity of a single cell in certain arrangements of surfaces related to motion planning
Discrete and Computational Geometry 11 (1994), 1-33
A preliminary version appeared in Proc. 7th ACM  Symposium on Computational Geometry, North Conway, 1991, pp. 314-323.
[BibTex]

D. Halperin and M. Sharir
On disjoint concave chains in arrangements of (pseudo) lines
Information Processing Letters 40 (1991), 189-192.
Corrigendum
ibid 51 (1994),53-56.
[BibTex]



Robotics

R. Wein, J.P. van den Berg, and D. Halperin
Planning near-optimal corridors amidst obstacles (full version: Planning high-quality paths and corridors amidst obstacles)
Proc. 7th International Workshop on the Algorithmic Foundations of Robotics, New York City, July 2006.
[BibTex]

R. Wein, J.P. van den Berg, and D. Halperin
The visibility-Voronoi complex and its applications
Computational Geometry: Theory and Applications, 36 (1) 2007, pp. 66-87.
A preliminary version appeared in Proc. 21st ACM Symposium on Computational Geometry, Pisa, June 2005, 63-72.
[BibTex]

D. Halperin, L. Kavraki, and J.-C. Latombe,
Robotics
CRC Handbook of Discrete and Computational Geometry, 2nd Edition, J.E. Goodman and J. O'Rourke (eds.), CRC Press, Inc., Boca Raton, FL, 2004, pp. 1065-1093.
[BibTex]

O. Ilushin, G. Elber, D. Halperin and R. Wein and M.-S. Kim
Precise global collision detection in multi-axis NC-machining
Computer-Aided Design, 37(9), 2005, pp. 909-920.
A preliminary version appeared in Proc. International CAD Conference, Thailand, May 2004, pp. 233-243.
[BibTex]

R. Wein, O. Ilushin, G. Elber and D. Halperin
Continuous path verification in multi-axis NC-machining
International Journal of Computational Geometry and Applications, 15 (4) 2005, pp. 351-378. Special issue, dedicated to papers from the 20th ACM Symposium on Computational Geometry,
Brooklyn, June, 2004.
A preliminary version appeared in Proc. 20th ACM Symposium on Computational Geometry, Brooklyn, June 2004, pp. 86-95.
[BibTex]

S. Hirsch and D. Halperin
Hybrid motion planning: Coordinating two discs moving among polygonal obstacles in the plane
Proc. 5th Workshop on Algorithmic Foundations of Robotics (WAFR), Nice, 2002, 225-241.
[BibTex]

D. Halperin, M. Sharir and K. Goldberg
The 2-center problem with obstacles
Journal of Algorithms 42 (2002), pp. 109-134.
A preliminary version appeared in Proc. 16th ACM Symposium on Computational Geometry, Hong Kong, 2000,  80-90.
[BibTex]

D. Halperin, J.-C. Latombe and R.H. Wilson
A general framework for assembly planning: The motion space approach
Algorithmica , 26 (2000), 577--601
A preliminary version appeared in Proc. 14th ACM  Symposium on Computational Geometry , Minneapolis, 1998, 9-18.
[BibTex]

K.F. Böhringer, B.R. Donald and D. Halperin
Full version: On the area bisectors of a polygon
appeared in: Discrete and Computational Geometry, 22 (1999), 269-285.
A preliminary version entitled: The area bisectors of a polygon and force equilibria in programmable vector fields
appeared in: Proc. 13th ACM Symposium on Computational Geometry, Nice, 1997, pp. 457-459.
[BibTex]

D. Halperin, L. Kavraki, and J.-C. Latombe,
Robot algorithms
CRC Algorithms and Theory of Computation Handbook M. Atallah (editor), CRC Press, Inc., Boca Raton, FL, 1999, Chapter 21
[BibTex]

L.J. Guibas, D. Halperin, H. Hirukawa, J.-C. Latombe and R.H. Wilson
Polyhedral assembly partitioning using maximally covered cells in arrangements of convex polytopes
Int. J. of Computational Geometry and its applications, 8(2), 1998, 179-199.
A preliminary version appeared in Proc. IEEE International Conference on Robotics and Automation, Nagoya, Japan, 1995, 2553-2560.
[BibTex]

J. Chen, K. Goldberg, M. Overmars, D. Halperin, K.F. Böhringer, and Y. Zhuang
Computing tolerance parameters for fixturing and feeding
The Assembly Automation Journal , 22 (2002), 163-172.
A preliminary version entitled: Shape Tolerance in Feeding and Fixturing,  appeared in:
The Algorithmic Foundations of Robotics, P.K. Agarwal, L. Kavraki, and M. Mason, Eds., A.K. Peters, Boston, MA, 1998, 297-311.
[BibTex]

D. Halperin and R.H. Wilson
Assembly partitioning along simple paths: The case of multiple translations
Advanced Robotics , 11 (1997), 127-146.
A preliminary version appeared in IEEE International Conference on Robotics and Automation, Nagoya, Japan, 1995, 1585-1592.
[BibTex]

D. Halperin and C.-K. Yap
Combinatorial complexity of translating a box in polyhedral 3-space
Computational Geometry: Theory and Applications, 9 (1998), 181-196.
A preliminary version appeared in Proc. 9th ACM  Symposium on Computational Geometry, San Diego, 1993, pp. 29-37.
[BibTex]

D. Halperin and M. Sharir
A near-quadratic algorithm for planning the motion of a polygon in a polygonal environment
Discrete and Computational Geometry, 16 (1996), 121-134.
A preliminary version appeared in Proc. 5th Annual Symposium on Foundations of Computer Science (FOCS), Palo Alto, 1993, 382-391.
[BibTex]

P. Agarwal, M. de Berg, D. Halperin and M. Sharir
Efficient generation of k-directional assembly sequences
Proc. 7th ACM-SIAM Symp. on Discrete Algorithms (1996), 122-131.
[BibTex]

K.Y. Goldberg, D. Halperin, J.-C. Latombe and R.H. Wilson (editors)
Algorithmic Foundations of Robotics
A.K. Peters, Wellseley, MA, 1995.
[BibTex]

M. de Berg, L.J. Guibas, D. Halperin, M.H. Overmars, O. Schwarzkopf, M. Sharir and M. Teillaud
Reaching a goal with directional uncertainty
Theoretical Computer Science 140 (1995), 301-317.
A preliminary version appeared in Proc. 4th International Symposium on Algorithms and Computation (ISAAC '93), Hong Kong, 1993, 1-10.
[BibTex]

D. Halperin
Robot motion planning and the single cell problem in arrangements
Journal of Intelligent and Robotic Systems 11 (1994), 45-65.
[BibTex]

A.F. van der Stappen, D. Halperin and M.H. Overmars
The complexity of the free space for a robot moving amidst fat obstacles
Computational Geometry: Theory and Applications 3 (1993), 353-373.
[BibTex]

A.F. van der Stappen, D. Halperin and M.H. Overmars
Efficient algorithms for exact motion planning amidst fat obstacles
Proc. IEEE International Conference on Robotics and Automation, Atlanta, 1993, Vol. 1, pp.297-304.
[BibTex]

D. Halperin
Algorithmic motion planning via arrangements of curves and of surfaces
Ph.D Thesis, Computer Science Department, Tel Aviv University, Tel Aviv, July 1992.
[BibTex]

D. Halperin, M.H. Overmars and M. Sharir
Efficient motion planning for an L-shaped object
SIAM Journal on Computing 21 (1992), 1-23
A preliminary version appeared in Proc. 5th ACM Symposium on Computational Geometry, Saarbrücken, 1989, pp. 156-166.
[BibTex]

D. Halperin and M. Sharir
Improved combinatorial bounds and efficient techniques for certain motion planning problems with three degrees of freedom
Computational Geometry: Theory and Applications 1 (1992), 269-303.
A preliminary version appeared in Proc. 2nd Canadian Conference on Computational Geometry, Ottawa, 1998, pp. 98-101.
[BibTex]

D. Halperin
Automatic kinematic modelling of robot manipulators and symbolic generation of their inverse kinematics solutions
Proc. 2nd International Workshop on Advances in Robot Kinematics Linz, 1990. pp. 310-317.
[BibTex]



Molecular Modeling

A. Enosh, S. J. Fleishman, N. Ben-Tal and D. Halperin
Prediction and Simulation of Motion in Pairs of Transmembrane Alpha-Helices
Proc. 5th European Conference on Computational Biology - ECCB 2006 , Eilat, Israel, 2007.
[BibTex]

S. J. Fleishman, S.E. Harrington, A. Enosh, D. Halperin, C.G. Tate and N. Ben-Tal
Quasi-symmetry in the Cryo-EM Structure of EmrE Provides the Key to Modeling its Transmembrane Domain
Journal of Molecular Biology, 364 (2006), 54-67.
[BibTex]

E. Eyal and D. Halperin
Improved maintenance of molecular surfaces using dynamic graph connectivity
Proc. 5th International Workshop on Algorithms in Bioinformatics - WABI 2005 , Mallorca, Spain, 2005, Springer LNCS, Vol. 3692.
[BibTex]

E. Eyal and D. Halperin
Dynamic maintenance of molecular surfaces under conformational changes
Proc. 21st ACM Symposium on Computational Geometry , Pisa, June 2005, 45-54.
[BibTex]

A. Enosh, S.J. Fleishma, N. Ben-Tal and D. Halperin.
Assigning transmembrane segments to helics in intermediate-resolution structures
Proc. Twelfth International Conference on Intelligent Systems for Molecular Biology (ISMB), held jointly with the Third European Conference on Computational Biology (ECCB),
Glasgow, July-August, 2004, pp. 122-129.
[BibTex]

I. Lotan, F. Schwarzer, D. Halperin and J.-C. Latombe
Algorithm and data structures for efficient energy maintenance during Monte Carlo simulation of proteins
Journal of Computational Biology 11 (5), 2004, 902-932.
A preliminary and partial version, titled: Efficient maintenance and self-collision testing for kinematic chains,
 appeared in Proc. 18th ACM Symposium on Computational Geometry, Barcelona, 2002, pp, 43-52.
[BibTex]

D. Halperin and C.R. Shelton
A perturbation scheme for spherical arrangements with application to molecular modeling
Computational Geometry: Theory and Applications 10 (4), 1998, 273-288.
(see also the section "Robust geometric computing" above)
A preliminary version appeared in Proc. 13th ACM  Symposium on Computational Geometry, Nice, 1997, 183-192.
[BibTex]

D. Halperin and M.H. Overmars
Spheres, molecules, and hidden surface removal
Computational Geometry: Theory and Applications 11 (2), 1998, 83-102.
A preliminary version appeared in Proc. 10th ACM  Symposium on Computational Geometry, Stony Brook, 1994, 113-122.
[BibTex]

P.W. Finn, D. Halperin, L. Kavraki, J.-C. Latombe, R. Motwani, C.Shelton, and S. Venkatasubramanian
Geometric manipulation of flexible ligands
Applied Computational Geometry: Towards geometric Engineering M.C. Lin and D. Manocha (editors), Springer 1996, (papers from the ACM Workshop on Applied Computational Geometry 1996), pp. 67-78.
[BibTex]

D. Halperin, J.-C. Latombe, and R. Motwani
Dynamic maintenance of kinematic structures
Algorithms for Robotic Motion and manipulation (WAFR '96), J.-P. Laumond and M. Overmars (editors), A.K. Peters, Wellesley, 1997, pp. 155-170
A preliminary version appeared in Proc. 2nd Workshop on the Algorithmic Foundations of Robotics, Toulouse, 1996.
[BibTex]



Miscellaneous

B. Aronov, H. Brönimann, D. Halperin and R. Schiffenbauer
On the number of views of polyhedral scenes
Revised Papers of the Japanese Conference on Discrete and Computational Geometry (JCDCG 2000) , Tokai University, Japan, October 2000. Springer LNCS Vol. 2098, pp. 81-90.
[BibTex]

D. Cohen-Or, G. Fibich, D. Halperin and E. Zadicario
Conservative visibility and strong occlusion for viewpsace partitioning of densely occluded scenes
Eurographics '98, Computer Graphics Forum 17 (3) (1998), C243-C253.
[BibTex]

M. Charikar, D. Halperin and R.Motwani
The dynamic servers problem
Proc. 9th ACM Symposium on Discrete Algorithms (SODA), San Francisco, 1998, pp. 410-419.
[BibTex]

H.K. Ahn, M. de Berg, P. Bose, S.W. Cheng, D. Halperin, J. Matousek, and O. Schwarzkopf
Separating an object from its cast
Computer-Aided Design, 34 (8), 2002, pp. 547-559.
A preliminary version appeared in Proc. 13th ACM Symposium on Computational Geometry, Nice, 1997, pp. 221--230.
[BibTex]

M. de Berg, D. Halperin, M.H. Overmars, J. Snoeyink and M. van Kreveld
Efficient ray shooting and hidden surface removal
Algorithmica 12 (1994), 30-53.
A preliminary version appeared in Proc. 7th ACM  Symposium on Computational Geometry, North Conway, 1991, pp. 21-30.
[BibTex]



Surveys

E. Fogel, D. Halperin, L. Kettner, M. Teillaud, R. Wein and N. Wolpert
Arrangements
Effective Computational Geometry for Curves and Surfaces, Jean-Daniel Boissonnat and Monique Teillaud (eds.), Springer, Mathematics and Visualization series, 2007, Chapter 1, pp. 1-66.
[BibTex]

D. Halperin
Arrangements
CRC Handbook of Discrete and Computational Geometry, 2nd Edition, J.E. Goodman and J. O'Rourke (eds.), CRC Press, Inc., Boca Raton, FL, 2004, pp. 529-562.
[BibTex]

D. Halperin, L. Kavraki, and J.-C. Latombe,
Robotics
CRC Handbook of Discrete and Computational Geometry, 2nd Edition, J.E. Goodman and J. O'Rourke (eds.), CRC Press, Inc., Boca Raton, FL, 2004, 1065-1093.
[BibTex]

D. Halperin
Robust geometric computing in motion
Algorithmic and Computational Robotics: New Dimensions (WAFR '00). B.R. Donald and K.M. Lynch and D. Rus (eds.,) A.K. Peters,
Wellesley, 2001, pp. 9-22.
(Invited talk at WAFR 2000, Workshop on Algorithmic Foundations of Robotics , Dartmouth College, March 2000).
[BibTex]

D. Halperin, L. Kavraki, and J.-C. Latombe,
Robot algorithms
CRC Algorithms and Theory of Computation Handbook M. Atallah (editor), CRC Press, Inc., Boca Raton, FL, 1999, Chapter 21
[BibTex]

D. Halperin and M. Sharir
Arrangements and their applications in robotics: Recent developments
The Algorithmic Foundations of Robotics, K. Goldberg, D. Halperin, J.C. Latombe and R. Wilson, Eds., A.K. Peters, Boston, MA, 1995, 495-511.
A preliminary version appeared in Proc. 1st Workshop on the Algorithmic Foundations of Robotics, San Francisco, 1994.
[BibTex]

D. Halperin
Robot motion planning and the single cell problem in arrangements
Journal of Intelligent and Robotic Systems 11 (1994), 45-65.
[BibTex]


danha@post.tau.ac.il, June 27th, 2004