Freda, J.; Sadinski, W. J.; Dunson, W. A. (1991). "Long term monitoring of amphibian populations with respect to the effects of acidic deposition". Water, Air, & Soil Pollution. 55 (3–4): 445–462. Bibcode:1991WASP...55..445F. doi:10.1007/bf00211205. S2CID85373859.
Freda, J.; Sadinski, W. J.; Dunson, W. A. (1991). "Long term monitoring of amphibian populations with respect to the effects of acidic deposition". Water, Air, & Soil Pollution. 55 (3–4): 445–462. Bibcode:1991WASP...55..445F. doi:10.1007/bf00211205. S2CID85373859.
Freda, J.; Sadinski, W. J.; Dunson, W. A. (1991). "Long term monitoring of amphibian populations with respect to the effects of acidic deposition". Water, Air, & Soil Pollution. 55 (3–4): 445–462. Bibcode:1991WASP...55..445F. doi:10.1007/bf00211205. S2CID85373859.