“…While this is largely due to the absence of a proper mathematical definition of multigraphs (or multiplex graphs), the possibility and implications of having two or more types of links were approached by sociologists since the 1960s (Mitchell, 1969;Burt, 1992;Eve, 2002), notably looking at the effects of having both personal and professional relations within a given organization on individuals' career evolution. Such multiedge relations are thus called two-dimensional in social network analysis in opposition to singlestranded edges or links (Larson and Starr, 1993 ;Degenne and Forsé, 1999); they sometimes allow directionality (multidigraph) and the existence of loops, self-loops, or self-edges (pseudograph).…”