Ross indexed the following pages under the keyword: "Accessible state".

Summary: "Stability"defined. A "machine" is a stable sub-set. 4630, 4632, 4643, 4656, 4795 Summary: Every set in a machine generates a stable set that contains it. 4630 Accessible state Stable set generated by set Variety in set theory 4624 4625

Summary: On the accessibility of states. 4953, 4968 Accessible state Control of system Initial state control over Machine partly observable Summary: The "partly observable machine with input." 4956 Epistemology [45]: "Observing" or "studying" a machine means getting sequence of inputs and outputs alternately, 4953. 4952 4953