@article{Kroft1967b, 
     author = "Kroft, D.", 
     doi = "10.1109/PROC.1967.5389", 
     issn = "0018-9219", 
     journal = "Proceedings of the IEEE", 
     link = "http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=1447319", 
     month = "jan", 
     number = "1", 
     pages = "88--90", 
     title = "All paths through a maze", 
     uri = "http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=1447319", 
     volume = "55", 
     year = "1967", 
}

Problems: 422