Stephen Nelson Stephanie Balzer Gavin M. Bierman Erik Meijer James Noble David J. Pearce Jiri Soukup Frank Tip Relationships and associations in object-oriented languages. 855-856 2008 OOPSLA Companion http://doi.acm.org/10.1145/1449814.1449883 conf/oopsla/2008c db/conf/oopsla/oopsla2008c.html#NelsonBBMNPST08