International Journal of Supply and Operations Management 1 2 2014 08 01 Inventory Model for Deteriorating Items with Four level System and Shortages216 227 en Rakesh Prakash Tripathi Graphic Era University, Dehradun (UK) India 2014 05 29 Inventory Constant demand Deterioration Shortages Production http://www.ijsom.com/pdf_2048_23744adecf6428f88d10639e6e328f18.html