The list have been compiled by Jeff Sauro and published on Mesiuring Usuability blog on 7th of July 2010. The article is worth reading as I'm posting here only excerpts without any comments and descriptions.
1. Designing for usability: key principles and what designers think. Gould, J. D. and Lewis, C. (1985) View Paper [pdf]
Two honorable mentions for pioneering work include:
Al-Awar, J., Chapanis, A., and Ford, R. (1981). Tutorials for the first-time computer user.
IEEE Transactions on Professional Communication, 24, 30-37. This is one
of the first descriptions of formative usability testing. Prior to this
paper most user testing efforts were more summative (benchmark
Shackel, B. (1990). Human factors and usability.
In J. Preece and L. Keller (Eds.), /Human-Computer Interaction,
Selected Readings/ (pp. 27-41). This paper defined usability as a
function of efficiency, effectiveness & satisfaction (the ISO 9241
pt 11 standard). Despite many proposed extensions, we still think of usability in terms of these three aspects
2. Heuristic evaluation of user interfaces, Nielsen, J., and Molich, R. (1990) View Paper[pdf]
3. Damaged merchandise? A review of experiments that compare usability evaluation methods. Gray, W. D., and Salzman, M. C. (1998). View Paper[pdf]
4. Refining the test phase of usability evaluation: how many subjects is enough?. Virzi, R. A. (1992) View Paper [Paid Link]
Other Honorable mentions in this category include:
Lewis, James (1982) "Testing Small System Customer Setup [pdf]
in Proceedings of the Human Factors Society 26th Annual Meeting p.
718-720 (1982).This is probably the first to use the binomial for
usability problem discovery.
5. Comparative Evaluation of Usability Tests Molich et al (1998). View Paper [pdf]
Jacobsen, N. E., Hertzum, M., & John, B. E. (1998) "The Evaluator Effect in Usability Tests [pdf]:
Problem Detection & Severity Judgments" in Proceedings of the Human Factors Society 42nd Annual Meeting p. 1336-1340