Recursive Solution of a Class Of Combinatorial Problems: An Example
Combinatorial problems requiring the selection
of n elements from a set of m elements may be 
solved by a recursion process analogous to that for
computing binomial coefficients.  Several specific 
problems are analyzed, the general technique is exposed,
and an ALGOL program is developed for one of 
the problems.
CACM October, 1965
Lynch,W. C.
