On Maintenance of the Opportunity List
for Class-Teacher Timetable Problems
One of the principal components of procedures
for the solution of class-teacher timetable problems 
is that for maintenance of the opportunity list.  Opportunity
list maintenance methods are based on necessary 
conditions for the existence of a solution. A general
framework for necessary conditions, together with 
four specific sets of necessary conditions, is given.
CACM April, 1975
Smith, G.
