“…To name a few, we mention the "mode summation technique" [12,13,17,18] (which was the method originally used by Casimir), analyses of Green's functions and of the energy-momentum tensor in the presence of boundaries [20,21,22,23,24,25,26] and zeta function techniques [27,28]. These techniques possess flexibility which permits, among other things, the handling of temperature dependence (in vacuum and in dielectrics) [20,21,26,29,30,31,32,34], of fields with finite mass [31,35], various geometrical setups [5,6,7,8,22,24,25,32,33,36,37], and a better insight into the Casimir force (macroscopic) in relation to microscopic "long range forces" [14].…”