"Fundamental Concepts in Programming Languages" (1967, available online at http://www.wkap.nl/sampletoc.htm?1388-3690+13+1/2+2000 )
This seminal paper by ChristopherStrachey discusses notions of assignment, including LeftValues and RightValues. It also coined the terms ParametricPolymorphism and AdHocPolymorphism.
CategoryPaper CategoryPolymorphism
Does anyone have a link to Strachey's paper (mentioned above) that works? --PeterGoodall
Found at http://www.is.pku.edu.cn/~qzy/plan/lits/FundamentalConceptOfPL.pdf (2006.08.30) (still good 2009.05.22) (Dead, 2011.05.12)
And re-found at http://www.itu.dk/courses/BPRD/E2009/fundamental-1967.pdf (2011.09.06) (and still alive 2014.05.21)
See also the links on LeftValue and RightValue