Relative Identity - The view that there are objects which are the same F yet not the same G; from the Stanford Encyclopedia by Harry Deutsch. plato.stanford.edu/entries/identity-relative
The Identity of Indiscernibles - Entry by Peter Forrest in the Stanford Encyclopaedia of Philosophy. The principle is due to Leibniz, and states two entities are identical if they share the same properties. plato.stanford.edu/entries/identity-indiscernible
The Paradox of Identity - Report by William Greenberg. Argues for a Hegelian account of identity. structuredindividuals.com/paradox/toc.html