↑ Gallup, G.G., Jr., Nash, R.F., Potter, R.J. and Donegan, N.H., (1970). Effect of varying conditions of fear on immobility reactions in domestic chickens (Gallus gallus). Journal of Comparative and Physiological Psychology, 73: 442–445
↑ Gallup, G.G., Jr., (1979). Tonic immobility as a measure of fear in the domestic fowl. Animal Behaviour, 27: 316–317
↑ Jones, B. and Faure, J.M. (1981). Tonic immobility ("righting time") in laying hens housed in cages and pens. Applied Animal Ethology 7: 369–372