I added this to the digest so I'll toss in a few more bits.
Pot-Limit Omaha Poker by Jeff Hwang
How Good is Your Pot-Limit Omaha? by Stewart Reuben
Secrets of Professional Pot-Limit Omaha by Rolf Slotboom
Omaha Poker by Bob Ciaffone
Doyle Brunson's Super System 2: A Course in Power Poker by Doyle Brunson
Championship Omaha by Tom McEvoy and T.J. Cloutier (not recommended)
Hwang has nice sizes sections on LO8 and PLO8.
Ciaffone discuss LO8 and Limit Omaha high, as does the Cloutier book. Just like PLO, I think you get more out of the Hwang section for LO8. You'll probably never play Limit Omaha High in your life. There are currently 0 LO high games running on stars as I write this.
SS2 has a section on LO8 which is again OK but not worth buying the book just for that. But if you're the kind of person who would play LO8 and PLO I'd buy SS1 and SS2. Probably SS2 first. SS1 is a little dated, especially the stud lo section which was written before 8 or better was the standard.
Ray Zee's book is the only one I have read on LO8. It's excellent and as a b0nus you get Stud 8 as well.
High-Low-Split Poker, Seven-Card Stud and Omaha Eight-or-better for Advan (Advance Player) by Ray Zee