In "Disjoint Set Union" article you mention that "there are several articles disputing...[time complexity]", but somehow you don't mention, that at least the first article has been retracted, see discussion in wikipedia - https://en.wikipedia.org/wiki/Talk%3ADisjoint-set_data_structure#Hantao_Zhang_says_that_the_time_is_linear
(and I guess the second mentioned paper hasn't been peer-reviewed at all)