Such is the language, which from the Greek is taken to mean: "what must be shown was". This translation in some verses: "proof was what should (could)". The abbreviation of this sentence .q. e. d. Researchers and teachers, especially in science, mathematics and physics at the end of the proof of an issue, write qed. Nowadays, from this signal, together are used ■ or □, or ‣. In Fant : (U 220E) or (U 25A0) or (U, 2023). Mathematician, to mark this Cairn, they say.

Euclid and Archimedes proof of the issue of Hara with this sentence to the end of the season.

.q. e. d researchers and experts, with interpretation, the other from the Latin language, as the Joker also use. A Tabor quo errat demonstrator that means: "constant in the error, he started," and other quod est dubitandum, which says: "the thing about doubt is"