B. Thomas (1984) applies the term ESS to an individual strategy which may be mixed, and evolutionarily stable population state to a population mixture of pure strategies which may be formally equivalent to the mixed ESS.
Thomas (1984) mengaplikasikan istilah SSE ke strategi individu yang mungkin campuran, dan keadaan populasi stabil evolusioner terhadap suatu populasi campuran dari strategi murni yang mungkin secara formal sama dengan campuran SSE.