A Formulation and Defense of the Doctrine of the Trinity by William Lane Craig

http://www.reasonablefaith.org/a-formulation-and-defense-of-the-doctrine-of-the-trinity

See also Craig's Defenders Podcasts on the topics of:


Doctrine of God
(20 audio files)

Doctrine of the Trinity
(8 audio files)

Doctrine of Christ
(30 audio files)

Doctrine of the Holy Spirit

(5 audio files)