Voelkl J.E, Fries B.E, Galecki A.T.  1995.  Predictors of nursing home residents' participation in activity programs. Gerontologist. 35(1):44-51.

Voelkl J.E, Galecki A.T., Fries B.E..  1996.  Nursing home residents with severe cognitive impairments: predictors of participation in activity groups.. Therapeutic Recreation Journal. (First Quarter):27-40.