Reference for Keritot 36:11

אמר ר' זירא כאן שנה רבי

Raba said: Awareness of the doubt does not separate [the acts] for sin-offerings; but this is what he [Rabbi] meant to teach: Just as he would be liable to separate sin-offerings if he became aware [after each act] that th transgression was certain, so he is also liable to separate suspensive guilt-offerings, if he became each time aware of the doubt.

Jastrow