Rhet gre 1377b20-21ἀνάγκη μὴ μόνον πρὸς τὸν λόγον (21) ὁρᾶν, ὅπως ἀποδεικτικὸς ἔσται καὶ πιστός,
Rhys Roberts 1924 engthe orator must not only try to make the argument of his speech demonstrative and worthy of belief;
http://www2.hf.uio.no/common/apps/permlink/permlink.php?app=polyglotta&context=record&uid=cc2ab3e2-1d51-11e7-ba66-0050569f23b2