@article{Canfield1995, 
     author = "Canfield, E. Rodney and Williamson, S. Gill", 
     doi = "10.1007/BF01108590", 
     issn = "0167-8094", 
     journal = "Order", 
     link = "http://link.springer.com/10.1007/BF01108590", 
     number = "1", 
     pages = "57--75", 
     title = "A loop-free algorithm for generating the linear extensions of a poset", 
     uri = "http://link.springer.com/10.1007/BF01108590", 
     volume = "12", 
     year = "1995", 
}

Problems: 330