20th Century Schaff-Herzog Encyclopedia, pg. 1194,1195 "The pronunciation Yahweh of the Hebrew tetragrammaton need no longer be based on traditions preserved in late patristic sources. Both the vocalization yahwe and yahu (a shortened form used chiefly in personal names) are now confirmed by a variety of ancient Near Eastern inscriptional materials from the first and second millennia B.C."
The Modern Judaica Encyclopedia, Vol. 7, p.69 "The true pronunciation of the name YHWH was never lost. Several early Greek writers of the Christian Church testify that the name was pronounced 'Yahweh'. This is confirmed, at least for the vowels of the first syllable of the name, by the shorter form Yah, which is sometimes used in poetry (e.g., Ex.15:2) and the -yahu or -yah that serves as the final syllable in very many Hebrew names."
New Bible Dictionary (1962) " The pronounciation Yahweh is indicated by transliterations of the name into Greek in early Christian literature, in the form iaoue (Clement of Alexandria) or iabe (Theodoret; by this time Gk. b had the pronunciation of v)"