From BiblePortal Wikipedia

Smith's Bible Dictionary [1]

Jos'aphat. Jehoshaphat , king of Judah.  Matthew 1:8.

Holman Bible Dictionary [2]

 Matthew 1:8Jehoshaphat

Morrish Bible Dictionary [3]

Another form of Jehoshaphat.  Matthew 1:8 .

International Standard Bible Encyclopedia [4]

jos´a - fat ( Ἰωσαφάτ , Iōsaphát , the King James Version in   Matthew 1:8 for Jehoshaphat (which see)): A king of Judah, mentioned in Matthew's genealogy of Christ.

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [5]

( Ι᾿Ωσαφάτ ), a Graecized form ( Matthew 1:8) of the name of JEHOSHAPHAT (See Jehoshaphat) (q.v.), king of Judah.