A LISP Garbage-Collector for Virtual-Memory Computer Systems
In this paper a garbage-collection algorithm
for list-processing systems which operate within 
very large virtual memories is described.  The object
of the algorithm is more the compaction of active 
storage than the discovery of free storage.  Because free
storage is never really exhausted, the decision 
to garbage collect is not easily made; therefore,
various criteria of this decision are discussed.
CACM November, 1969
Fenichel, R. R.
Yochelson, J. C.
