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'''Michael Levin''',<br/>an American computer scientist, in the 60s affiliated with [[Massachusetts Institute of Technology]], and involved in the initial development of [[Lisp]] within the group of [[John McCarthy]]. The 1961 memo on [[Alpha-Beta]] by [[Daniel Edwards]] and [[Timothy Hart]] <ref>[[Daniel Edwards]] and , [[Timothy Hart]] ('''1961'''). ''The Alpha-Beta Heuristic'', AIM-030, reprint available from [http://dspace.mit.edu/handle/1721.1/6098 DSpace] at [[Massachusetts Institute of Technology|MIT]]</ref>, contains a Theorem by Michael Levin, the well known formula of the number of [[Leaf Node|leaf nodes]] that need to be examined in Alpha-Beta.

'''Theorem''' (Levin): <br/>Let '''''n''''' be the number of plies in a tree, and let '''''b''''' be the number of branches a every branch point. Then the number of terminal points on the tree is

* [[John McCarthy]], [[Paul W. Abrahams]], [[Daniel Edwards|Daniel J. Edwards]], [[Timothy Hart|Timothy P. Hart]], [[Michael Levin|Michael I. Levin]] ('''1962'''). ''LISP 1.5 Programmer's Manual.'' The M.I.T. Press, second edition (1985) available as [http://www.softwarepreservation.org/projects/LISP/book/LISP%201.5%20Programmers%20Manual.pdf pdf reprint] <ref>[http://www.softwarepreservation.org/projects/LISP/book/LISP%201.5%20Programmers%20Manual.pdf/view McCarthy et al. LISP 1.5 Programmer's Manual.] from [[The Computer History Museum]] Software Preservation Group</ref>