1. S.C. Shapiro, ed., Beam search, Encyclopedia of Artificial Intelligence 1, pp. 56–58.
2. Bidirectional heuristic search again;De Champeaux;J. ACM,1983
3. An improved bidirectional heuristic search algorithm;De Champeaux;J. ACM,1977
4. Depth first iterative deepening: An optimal admissible tree search;Korf;AI J.,1985
5. Principles of Artificial Intelligence;Nilsson,1980