@article{Pallo1986, 
     author = "Pallo, J. M.", 
     doi = "10.1093/comjnl/29.2.171", 
     issn = "0010-4620", 
     journal = "The Computer Journal", 
     month = "feb", 
     number = "2", 
     pages = "171--175", 
     title = "Enumerating, Ranking and Unranking Binary Trees", 
     volume = "29", 
     year = "1986", 
}

Problems: 480