15(2), 101 (1970). (2) هل الرقم ستة كبير أم صغير؟

The problem of Erdős numbers has been studied extensively by the mathematician Jerry Grossman, who maintains a Web page on the subject at

http://www.oakland.edu/~grossman/erdoshp.html . An early summary of his work is: ⋆⋆ Grossman, J. W., and Ion, P. D. F. On a portion of the well-known collaboration graph.

Congressus Numerantium,

108, 129-131 (1995).

Some more recent work on Erdős numbers is by: ⋆⋆ Batagelj, V., and Mrvar, A. Some analyses of Erdős collaboration graph.

Social Networks,

22(2), 173-186 (2000).

Other evidence that small-world networks can make problem-solving harder, rather than easier, is presented in: • Walsh, T. Search in a small world. In

Conference on Artificial Intelligence (Morgan Kaufmann, San Francisco 1999), pp. 1172-1177. (3) مشكلة البحث في مسألة العالم الصغير

Bog aan la aqoon