Wheeler, Kevin. Medieval Numerology: A Brief Guide. Medievel Literature Resources. Carson-Newman College. 2012. Web. 8 Oct. 2012. http://web.cn.edu/KWHEELER/documents/Numerology.pdf (Good starting point)
Cusimano, Alessandra Carmen. Importance of Medieval Numerology and the Effects Upon Meaning in the Works of the Gawain-Poet: A Thesis. New Orleans, U of New Orleans. 2010 Web. 7 Oct 2012. http://louisdl.louislibraries.org/cdm/ref/collection/NOD/id/1047
Eckhardt, Caroline D. Essays in the Numerical Criticism of Medieval Literature. Lewisburg, 1980. Web. 7 Oct 2012.
Howard, Donald R. "Structure and Symmetry in Sir Gawain." Speculum. (July 1964) 39.3 pp. 425–433. Web. 7 Oct 2012. http://www.english.uga.edu/~jdmevans/Personal/howardgawain.pdf (five is presented in this article)