x1 is a [physical] page/leaf of book/document/bound mass of pages x2.
Numbered pages (as in a book) are the sides of a page (= paprysfe, paprysfelai); a pageful of text (= papryseltcidu, paprytcidylai). See also karni, pelji, prina, xatra, vreji, pezli, cukta, ciska.