The following is a list of LENS (Low Energy Neurofeedback System) studies and references.  Some of the studies reference predecessors to the LENS, such as FNS (Flexyx Neurotherapy System).  This list has been made available thanks to Dr. Corydon Hammond, and several studies cited here are published in his book, LENS: The Low Energy Neurofeedback System.

Cripe, C. T. (2006). Effective use of LENS unit as an adjunct to
cognitive neuro-developmental training. Journal of Neurotherapy,
10(2-3), 79-87.

Donaldson, C. C. S., Sella, G. E., & Mueller, H. H.
(1998). Fibromyalgia: A retrospective study of 252 consecutive
referrals. Canadian Journal of Clinical Medicine, 5 (6), 116-127.

Esty, M. L. (2006). Reflections on FMS treatment, research, and
neurotherapy: Cautionary tales. Journal of Neurotherapy, 10(2-3), 63-68.

Hammond, D. C. (Ed.). LENS: The Low Energy Neurofeedback
System. Binghampton, NY: Haworth Medical Press.

Kravitz, H. M., Esty, M. L., Katz, R. S., & Fawcett, J.
(2006). Treatment of fibromyalgia syndrome using low-intensity
neurofeedback with the Flexyx Neurotherapy System: A randomized
controlled clinical trial. Journal of Neurotherapy, 10(2-3), 41-58.

Larsen, S. (2006). The healing power of neurofeedback. Rochester,
VT: The Healing Arts Press.

Larsen, S., Harrington, K., & Hicks, S. (2006). The LENS (Low Energy
Neurofeedback System): A clinical outcomes study of one hundred
patients at Stone Mountain Center, New York. Journal of
Neurotherapy, 10(2-3), 69-78.

Larsen, S., Larsen, R., Hammond, D. C., Sheppard, S., Ochs, L.,
Johnson, S., Adinaro, C., & Chapman, C. (2006). The LENS
neurofeedback with animals. Journal of Neurotherapy, 10(2-3), 89-104.

Mueller, H. H., Donaldson, C. C. S., Nelson, D. V., & Layman, M.
(2001). Treatment of fibromyalgia incorporating EEG-driven
stimulation: A clinical outcomes study. Journal of Clinical
Psychology, 57(7), 933-952.

Ochs, L. (2006). The Low Energy Neurofeedback System (LENS): Theory,
background, and introduction. Journal of Neurotherapy, 10(2-3), 5-39.

Ochs, L. (2006). Comment on the treatment of fibromyalgia syndrome
using low-intensity neurofeedback with the Flexyx Neurotherapy
System: A randomized controlled clinical trial, or how to go crazy
over nearly nothing. Journal of Neurotherapy, 10(2-3), 59-61.

Schoenberger, N. E., Shiflett, S. C., Esty, M. L., Ochs, L., &
Matheis, R. J. (2001). Flexyx neurotherapy system in the treatment
of traumatic brain injury: An initial evaluation. Journal of Head
Trauma Rehabilitation, 16(3), 260-274.