@article{Saitoh2010a, 
     author = "Saitoh, Toshiki and Yamanaka, Katsuhisa and Kiyomi, Masashi and Uehara, Ryuhei", 
     doi = "10.1587/transinf.E93.D.1816", 
     isbn = "3642002013", 
     issn = "09168532", 
     journal = "IEICE Transactions on Information and Systems", 
     keyword = "Counting,Enumeration,Proper interval graphs,Random generation,Unit interval graphs", 
     link = "http://search.ieice.org/bin/summary.php?id=e93-d_7_1816\&category=D\&year=2010\&lang=E\&abst=", 
     month = "jul", 
     number = "7", 
     pages = "1816--1823", 
     publisher = "The Institute of Electronics, Information and Communication Engineers", 
     title = "Random generation and enumeration of proper interval graphs", 
     uri = "http://search.ieice.org/bin/summary.php?id=e93-d_7_1816&category=D&year=2010&lang=E&abst=", 
     volume = "E93-D", 
     year = "2010", 
}

Problems: 123