Bibliography:
-------------

Ideas for the backtracking swapping algorithm:

[1] Michael Marte - Models And Algorithms For School Timetabling - 
A Constraint Programming Approach - (free, on the internet, I lost the link)
 - Section 2.2.5 - Manual Timetabling - pages 23-24.

[2] Jantien Hartog - Timetabling on Dutch High-Schools - 
Satifiability versus gp-Untis (free, on the internet, I lost the link)
 - Section 5.2 - page 27.
