Terms for subject Mathematics containing when and only when

English	Russian
many tables of values for special functions could be calculated at a time when pencil and paper were the only available орудия	единственно доступные инструменты
many tables of values for special functions could be calculated at a time when pencil and paper were the only available tools	единственно доступные инструменты
when and only when	когда и только когда
when and only when	тогда и только тогда