“…It could be said that the research situation is quite rich, in the following sense. Whereas Euler's original evaluations, of which ζ(4, 1) = 2ζ(5) − ζ(2)ζ (3) is exemplary, along with more modern evaluations such as: ζ(4, 5, 1) = 2ζ(7, 3) + ζ(5) 2 − 17ζ(3)ζ(7) + ζ(2)ζ(5, 3) + 10ζ(2)ζ(3)ζ(5) − 21 20 ζ(10), ζ(6, 6, 6, 6) = 4π 24 432684797065192546875 , are now proved (Markett [13], Borwein and Girgensohn [8], Borwein et al [7]), suspected evaluations such as Zagier's conjectured: ζ(3, 1, 3, 1, ..., 3, 1) = 2π 4n (4n + 2)! (where n denotes the the number of (3, 1) pairs) remain elusive.…”