Johnson, J.S.; Newport, E.L. (1991). "Critical Period Effects on Universal Properties of Language: The Status of Subjacency in the Acquisition of a Second Language. Cognition. 39. pp. 215–258. دُوِي:10.1016/0010-0277(91)90054-8.
Foster, T.; Gillespie, K.; McClelland, R. (1997). "Mental Disorders and Suicide in Northern Ireland". British Journal of Psychiatry. 170(5). pp. 447-452. دُوِي:10.1192/bjp.170.5.447.