sentences:  These strategies were created with the aim to save costs, and therefore Zinn and Bowersox (1988) created a useful cost-model to see how postponement affects each strategy with regards to costs
  
  After the development of postponement concept in the 20th century, researchers started defining postponement differently today and there are two key developments in 2001 and 2004.Van Hoek in 2001 claimed that it is important to analyze postponement not just on the marketing and distribution channel levels but also on the supply chain level.He argued that previous theories developed in the 20th century had gaps in their research of postponement, and, therefore, Van Hoek identified 5 challenges