“…This is currently a very active research area where considerable progress has been made (e.g., the recent work of Vyatkin and Martinez Lastra [20], Batista et al [21], Schwab et al [22], Thramboulidis et al [23], Sivaharan et al [24], and Thramboulidis and Zoupas [25]). In order to focus our discussion and provide a flavour for the work in this area however, our overview is not intended to be …”