P. Kolaitis, R. Pichler, E. Sallinger, V. Savenkov:
"Nested dependencies: structure and reasoning";
in: "Proceedings of the 33rd ACM SIGMOD-SIGACT-SIGART Symposium on Principles of Database Systems, PODS'14, Snowbird, UT, USA, June 22-27, 2014", R. Hull, M. Grohe (ed.); ACM, 2014, 176 - 187.
http://doi.acm.org/10.1145/2594538.2594544