Bell, A. M. (1981). "Vergence: an evaluation". Journal of Structural Geology. 3 (3): 197–202. doi:10.1016/0191-8141(81)90015-8
Liotta, Domenico (2002). "D2 asymmetric folds and their vergence meaning in the Montagnola Senese metamorphic rocks (inner northern Apennines, central Italy)". Journal of Structural Geology. 24 (9): 1479–1490. doi:10.1016/S0191-8141(01)00145-6