Robert Shaw’s short 1 chapter work on God and the Holy Trinity is an excellent collection of observations and verses that defend the Trinity.
Warfield Biblical Doctrine of the Trinity is a short single chapter work (29 pgs) on different biblical aspects of the Trinity.
Presenting 49 Vital Doctrines of the Scriptures, Abbreviated and Simplified for Popular Use, Including Suggestive Questions on Each Topical and Textual Indices.
Dabney was a Baptist, and this work is his Systematic Theology. Dabney was also Calvinistic.
The Bible itself reveals those doctrines that are essential to the Christian faith. They are 1) the Deity of Christ, 2) Salvation by Grace, 3) Resurrection of Christ, 4) the gospel, and 5) monotheism. These are the doctrines the Bible says are necessary.
This small article could very well determine whether you are in or out of the Christian Faith
Litmus Test: You have to believe items 1-5 to be in the Christian Faith.
Carm’s work on the Trinity is a simple theWord module of Matthew Slick’s articles on the Trinity defending it.
Dr. Luginbill’s work, The Theology of God, treats basically the essence of God and the Persons of the Trinity. Although he only deals with these two issues technically, I have included a lot of appendices which come from emails he received and answered.