Add links to more garbage collection papers.

garbage_collection/README.md

@@ -1,2 +1,7 @@
 * [A Unified Theory of Garbage Collection](http://www.cs.virginia.edu/~cs415/reading/bacon-garbage.pdf)
+* [A LISP Garbage-Collector for Virtual-Memory Computer Systems](https://www.cs.purdue.edu/homes/hosking/690M/p611-fenichel.pdf)
+* [Incremental Collection of Mature Objects](http://pdf.aminer.org/000/465/194/incremental_collection_of_mature_objects.pdf)
 * :scroll: [Incremental Mature Garbage Collection Using the Train Algorithm](https://www.sics.se/~seif/DatalogiII/Book/train.ps)
+* [Incremental Garbage Collection: The Train Algorithm](http://www.ssw.uni-linz.ac.at/General/Staff/TW/Wuerthinger05Train.pdf)
+* [The Lisp II Garbage Collector](ftp://publications.ai.mit.edu/ai-publications/pdf/AIM-019.pdf)
+* [The Treadmill: Real-Time Garbage Collection Without Motion Sickness](http://home.pipeline.com/~hbaker1/NoMotionGC.html)