[headsupftw]

"Caught another mistake: Section 3.2: First, an observation: the column sums of Q(G) are all zero is wrong. Contradicts their definition of Q(G)." True, but it's pretty obvious he was referring to a directed graph G where matrix Q(G) is defined as Qij = 1 if vertex vi has an outgoing edge ej; -1 if vertex vi has an incoming edge ej; 0 otherwise.