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IN C.A. Bishop and K.E. Pettit, eds. Canadian Wildlife Service Occasional Paper Number 76, p. 10-13. Pechmann, J.H.K., Scott, D.E., Semlitsch, R.D., Caldwell, J.P., Vitt, L.J., and Gibbons, J.W., 1991. The problem of separating human impacts from natural fluctuations. Rouse, J.D., Bishop, C.A., and Struger, J., 1999.