Linda:
Besides the study we did at our center on hindmilk (Thanks Dr. Newman for
mentioning it!) I am not aware of any other studies investigating hindmilk
feeding. There are however several studies on fortified human milk feedings.
For instance:

Schanler, R & Garza, C. (1988).Improved mineral bablnce in very low birth
weight infants fed fortified human milk. J of Ped. 112(3):452-6.

Abrams, S., Schanler, R., Tsang, R. & Garza, C. (1989). Bone mineralization
in former very low birth weight infants fed either human milk or commercial
formula: One-year follow-up observation. J of Ped. 114(6):1041-4.

Sankaran, K, et al. (1996). A randomized, controlled evaluation of two
commercially available human breast milk fortifiers in healthy preterm
neonates. J Amer Diet Assoc. ,96(11):1145-9.

McClure, R. & Newell, S. (1996). Effect of fortifying breast milk on gastric
emptying. ADC., 74:F60-62.

To name a few. Hope this helps!

Nancy Hurst, RN, MSN
Lactation Program and Milk Bank
Texas Children's Hospital