One of the hidden gems in the L5 upgrade pkgs of Gold and higher is the 2900 page work An Exposition on Prayer in the Bible, by James Rosscup. http://www.logos.com/product/3440/an-exposition-on-prayer-in-the-bible
I was intrigued by this title when it was produced by Logos shortly after I began using Logos. It systematically covers every prayer in the Bible, book by book. It sounded interesting when it was released, but I wasn't sure how much use I would get out of $159.95 on prayer.
I checked to see what he had to say about prayer in Philemon this weekend, since I was wrapping up a study in that book with my SS class. He had 7 pages of tremendous material on prayer in that book of 25 verses.
I am convinced that I will find lots of valuable material for all my future SS lessons. I'm looking forward to benefiting from his study of prayer for 50 yrs.