From BiblePortal Wikipedia

Smith's Bible Dictionary [1]

Ra'gau. One of the ancestors of our Lord, son of Peleg.  Luke 3:35. He is the same person with Reu , son of Peleg. See Reu .

Fausset's Bible Dictionary [2]

 Luke 3:35. Ancestor of Jesus; equated to Reu, son of Peleg ( Genesis 9:19).

Holman Bible Dictionary [3]

 Luke 3:35

Hastings' Dictionary of the Bible [4]

Ragau . See following article.

Morrish Bible Dictionary [5]

See REU.

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [6]

( ῾Ραγαῦ ; Vulg. Ragau ), the Greek form of the name of a place and of a person.

1. A place named only in the Apocrypha ( Judith 1:5;  Judith 1:15). In the latter verse the "mountains of Ragau" are mentioned. It is probably identical with RAGES (See Rages) (q.v.).

2. One of the ancestors of our Lord, son of Phalec ( Luke 3:35). He is the same person with REU (See Reu) (q.v.), son of Peleg; and the difference in the name arises from our translators having followed the Greek form, in which the Hebrew ע was frequently expressed by Γ , as is the case in Raguel (which once occurs for Reuel), Gomorrha, Gotholiah (for Atholiah), Phogor (for Peor), etc.

International Standard Bible Encyclopedia [7]

rā´gô ( Ῥαγαῦ , Rhagaū́ (Westcott-Hort), Ῥαγαύ , Rhagaú  : the King James Version; Greek form of "Reu" (thus, the Revised Version (British and American)) (  Luke 3:35 ).