Citing abstract only papers/conference proceedings
It is a bit risky to cite papers having seen only the abstract. You might be able to contact the original authors in some cases for more complete versions. 

But, the safe and approved way to get access to papers that aren't easily available online, or available only by conflicting with with ethical considerations, is to go to your local library and ask the librarian there to get you a copy. Academic/university libraries are best, of course, but most libraries have some sort of access, directly or indirectly to nearly everything. 

Moreover, a research librarian at a good library is a tremendous resource for finding obscure things and even related things you don't know exist.