One of the core papers on concurrency. This is the one we used in 703, to talk about all the concurrency ideas. It's old, but the basic concepts still hold true.
@article{356903,
author = {Gregory R. Andrews and Fred B. Schneider},
title = {Concepts and Notations for Concurrent Programming},
journal = {ACM Comput. Surv.},
volume = {15},
number = {1},
year = {1983},
issn = {0360-0300},
pages = {3--43},
doi = {http://doi.acm.org/10.1145/356901.356903},
publisher = {ACM Press},
address = {New York, NY, USA},
}