@article{Knuth1974, 
     author = "Knuth, Donald E. and Szwarcfiter, Jayme L.", 
     doi = "10.1016/0020-0190(74)90001-5", 
     issn = "00200190", 
     journal = "Information Processing Letters", 
     keyword = "combinatorial problems,data structures,programming languages", 
     link = "http://www.sciencedirect.com/science/article/pii/0020019074900015 http://linkinghub.elsevier.com/retrieve/pii/0020019074900015", 
     month = "apr", 
     number = "6", 
     pages = "153--157", 
     title = "A structured program to generate all topological sorting arrangements", 
     uri = "http://www.sciencedirect.com/science/article/pii/0020019074900015", 
     volume = "2", 
     year = "1974", 
}

Problems: 78