I dont have reference, this is just logical "model" of sense amplifier. Typically no one commertial SRAM will not use something another, than analog SA, because penalty is speed, power consumption, reliability. Typical SA is designed in analog manner with carefull analog simulation of all corners timing, proper choice of transistor sizes (not minimal) to minimize offset, parasitics, using manualy optimized layout,... Above digital SA can be used if speed requirements are relaxed by a few times, comparing with custom designed analog SA.