$f$-Racks, $f$-Quandles, their Extensions and Cohomology
  The purpose of this paper is to introduce and study the notions of $f$-rack and $f$-quandle which are obtained by twisting the usual equational identities by a map. We provide some key constructions, examples and classification of low order $f$-quandles. Moreover, we define modules over $f$-racks, discuss extensions and define a cohomology complex for $f$-quandles. 
Indu R. U. Churchill, M. Elhamdadi, M. Green, A. Makhlouf
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