A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z

The theory that the Old Testament Book of Isaiah was written by two different authors and that chapters 1-39 were written by one author and 40-55 written by another. The latter chapters would be designated as Deutero-Isaiah. 

This theory, however, is incorrect. Isaiah was written by a single author.