@article{Er1987, 
     author = "Er, M. C.", 
     doi = "10.1093/comjnl/30.6.569", 
     issn = "0010-4620", 
     journal = "The Computer Journal", 
     link = "http://comjnl.oxfordjournals.org/cgi/doi/10.1093/comjnl/30.6.569", 
     month = "dec", 
     number = "6", 
     pages = "569--572", 
     title = "Lexicographic Listing and Ranking of T-Ary Trees", 
     uri = "http://comjnl.oxfordjournals.org/cgi/doi/10.1093/comjnl/30.6.569", 
     volume = "30", 
     year = "1987", 
}

Problems: 355