Gospel Guidebook: Getting and Keeping It Right 
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Articles on the Nature of God
Modalistic Monarchianism, Trinitarianism, and the Atonement
Modalistic Monarchianism Best Describes God's Nature
When Did "One God the Father" Become the "Triune God"?
Review of Simply Trinity by Matthew Barrett
Review of Delighting in the Trinity by Michael Reeves
Review of The Forgotten Trinity by James White
Articles, Books, Videos by Other People
The Acknowledgement and Proper Placement of the Distinction Between Father and Son by Jason Dulle (original link here)
The Incarnation of God and the Distinction between the Father and Son by Caleb Purstcher
Elohim Plural or Singular Part 1 by Nehemia Gordon
Elohim Plural or Singular Part 2 by Nehemia Gordon
Elohim Plurality and Attraction Part 3 by Nehemia Gordon
Did Constantine Write Matthew 28:19 into Our Bible? by Lon Martin
Is the Trinitarian Baptismal Formula of Matthew 28:19 an Interpolation? by F.C. Conybeare
The Word "Echad" in Deuteronomy 6:4
The Holy Spirit Today by Frank Stagg (see Ch. 1, pages 1-15)
Historical Books that Attest to Monarchianism
Truth Triumphs by Thomas Tomkinson in 1676 (see page 9 onward, especially pages 23-25)
A System of Religion by Thomas Tomkinson in 1729
The Muggletonian Principles Prevailing by Thomas Tomkinson in 1695
Divine Looking Glass by John Reeve and Lodowick Muggleton in 1661 (see pages 41 to 45)
An Introduction To The Early History Of Christian Doctrine by J.F. Bethune-Baker in 1903 (see pages 96 onward)
Notes On The Early History Of The Vulgate Monarchian Prologues by Dom John Chapman in 1908 (see pages 217 onward)
Jehovah-Jesus: The Oneness of God: The True Trinity by Robert Dodd Weekes in 1876