These are some of the free resources from Dr. Robert Morey on the Trinity. Both videos and articles:
Chapter Seven – A Multi-Personal God
God the Son in the Old Testament
Divine Angel and Eternal Spirit
Jesus Christ: The God Whose Glory Isaiah Beheld
David K. Bernard, J. L. Hall, Robert Morey, & Edgar Havaich Discuss Oneness Pentecostal Theology:
The Council 