Williams, C. A., & .Heins, R. M. (1981). Risk management and insurance (4th ed.). McGraw-Hill.

Williams, C. Arthur, and Richard M. .Heins. Risk Management and Insurance. 4th ed. New York: McGraw-Hill, 1981.

Williams, C. Arthur, and Richard M. .Heins. Risk Management and Insurance. 4th ed. McGraw-Hill, 1981.