@InProceedings{
   Lau:07,
   Author= "K.-K. Lau",
   Title = "Active Learning Sheets for A Beginner's Course on 
           Reasoning about Imperative Programs",
   Booktitle = "Proc. 38th {SIGCSE} Technical Symposium",
   Note= "ACM SIGCSE Bulletin, vol 39, no 1, March 2007",
   Publisher = "ACM Press", 
   Year = "2007
   Pages = "198-202"           }