Gospel of the Comforter by Steele is a 36 chapter work on the Holy Spirit and different aspects of Him (1897).
Cox details the evidence for the doctrine of the Trinity in the Bible looking dozens of different angles.
The Carnal Mind by Harmon Allen Baldwin is a 30 chapter work on the carnal mind, defining terms, biblical view, what is evil, guilt, pollution, self-denial, oppositon to light, etc.
Aitken Doctrine of Baptism is a 8 chapter work on baptism, looking at it from the consideration of Regeneration and Conversion.
Devotional Thoughts by Aitken is many chapter devotional work on various Christian life issues and topics.
CARM-Seventh Day Adventist by Matt Slick is a series of pages on this group as well as their version of Scripture, a Clear Word version.
This is a 17 page examination and defense of the doctrine of the Trinity. Alford examines Christ’s humanity as well as his divinity. Specifically Alford establishes Christ’s divine traits (omniscience, wisdom, omnipresence, immutability, omnipotence, equality with the Father, deity), and then he examines issues of the trinity, plurality of the Godhead, number of persons in the Godhead, the Father-Son-Spirit are one God. Then Alford examines the consequences of this doctrine, specifically in the light of the Unitarian’s denial of it, and finally Alford examines criticisms of the Trinity.