P.  Abrams, Menge, B., Mittelbach, G. G., Spiller, D., and Yodzis, P., ?The role of indirect effects in food webs?, in Food webs: integration of pattern and dynamics, G. A.  Polis and Winemiller, K. O., Eds. New York, NY: Chapman & Hall, 1995, pp. 371 - 395.