document.write("« What is the Wigner function closest to a given square integrable function?. (arXiv:1807.05635v1 [math-ph])");document.write(" | ");document.write("Wigner's type theorem in terms of linear operators which send projections of a fixed rank to projections of other fixed rank. (arXiv:1804.08156v2 [math.FA] UPDATED) »");