Ptak, C. A., & Schragenheim, E. (2004). ERP: : tools, techniques, and applications for integrating the supply chain (2nd edition.). St. Lucie Press.

Ptak, Carol A., and Eli Schragenheim. ERP: : Tools, Techniques, and Applications for Integrating the Supply Chain. 2nd edition. Boca Raton, Fluorida: St. Lucie Press, 2004.

Ptak, Carol A., and Eli Schragenheim. ERP: : Tools, Techniques, and Applications for Integrating the Supply Chain. 2nd edition. St. Lucie Press, 2004.