sentences:  The first quasi-set theory was proposed by D. Krause in his PhD thesis, in 1990 (see Krause 1992).A related physics theory, based on the logic of adding fundamental indistinguishability to equality and inequality, was developed and elaborated independently in the book "The Theory of Indistinguishables" by A. F. Parker-Rhodes.On the use of quasi-sets in philosophical discussions of quantum identity and individuality, see French (2006) and French and Krause (2006).