Reachability is harder for directed than for undirected finite graphsMiklos AjtaiRonald Fagin1987FOCS 1987Conference paper
Notes on searching in multidimensional monotone arraysAlok AggarwalJames Park1987FOCS 1987Conference paper
Results on learnability and the Vapnik-Chervonenkis dimensionNathan LinialYishay Mansouret al.1987FOCS 1987Conference paper