1. Bezpa, J., O. F. Johndrew, Jr., G. H. Thacker, R. M. Grover, F. V. Muir and C. A. Dupras, 1972. Field Studies on Egg Shell Damage and Bloodspot Detection. Rutgers University Extension Bulletin 403.
2. Observed egg shell damage in a mechanical gathering system;Eggleton;Poultry Sci.,1971
3. United States Department of Agriculture, 1974. Poultry and egg situation. Publication No. PES-284.