quod erat demonstrandum /erˈat dem-ən-stranˈdəm or dām-ōn-stranˈdŭm/

Which was to be proved or demonstrated (abbrev QED)

quod erat faciendum /fā-shē-enˈdəm or fa-ki-enˈdŭm/

Which was to be done (abbrev QEF)

quod erat inveniendum /in-vā-ni-enˈdəm/

Which was to be found (abbrev QEI)

quod vide /vīˈdē, viˈ or wiˈde/ (pl quae vide /kwē, kwī/)

Which see