code: private void remArc(int from, int to) throws ContradictionException {
  		if (from != to) {
  			for (int i : g.getMandSuccOrNeighOf(from)) {
  				if (g.removeArc(i, to, this)) {
  					arcRemoved(i, to);
  				}
  			}
  			for (int i : g.getMandPredOrNeighOf(to)) {
  				if (g.removeArc(from, i, this)) {
  					arcRemoved(from, i);
  				}
  			}
  		}
  	}
docs: --- Arc removals