1 Introduction  
2 Picking a single order on a single carousel  
2.1 The nearest-item heuristic  
2.2 The m-step strategy  
2.3 Optimal route  
2.4 Asymptotic results  
3 Multiple carousels: modeling challenges  
4 Related research areas  
4.1 Uniform spacings  
4.2 Exponential functionals of Poisson processes  
4.3 Lindley’s recursion  
4.4 The machine repair problem  
4.5 Rendezvous networks and layered queues  
4.6 Maximum weight independent sets in sparse random graphs  
5 Further research  
5.1 Considering different item storage schemes  
5.2 Further topics in two-carousel problems  
5.3 Extensions to multiple carousels  
5.4 Incorporating picking strategies to multiple carousel problems  
5.5 Considering the order arrival process  
5.6 Polling systems  
6 Literature overview  
6.1 Storage  
6.2 Picking a single order  
6.3 Picking multiple orders  
6.4 Design issues  
6.5 Problems involving multiple carousels