Summary: Almost two decades ago Ahlswede introduced an abstract correlated source \(({\mathcal V}\times{\mathcal W},{\mathcal S})\) with outputs \((v,w)\in{\mathcal S}\subset{\mathcal V}\times{\mathcal W}\), where persons \(P_{\mathcal V}\) and \(P_{\mathcal W}\) observe \(v\) and \(w\), respectively. More recently, Orlitsky considered the minimal number \(C_m\) of bits to be transmitted in \(m\) rounds to ``inform \(P_{\mathcal W}\) about \(v\) over one channel.'' He showed that \(C_2\leq 4C_\infty+3\) and that in general \(C_2\nsim C_\infty\). We give a simple example for \(C_3\nsim C_\infty\). However, for the new model ``inform \(P_{\mathcal W}\) over two channels,'' four rounds are optimal for this example -- a result we conjecture in general. If both \(P_{\mathcal V}\) and \(P_{\mathcal W}\) are to be informed over two channels about the other outcome, we determine asymptotically the complexities for all sources. In our last model ``inform \(P_{\mathcal V}\) and \(P_{\mathcal W}\) over one channel'' for all sources the total number \(T_2\) of required bits is known asymptotically and \(T_\infty\) is bounded from below in terms of average degrees. There are exact results for several classes of regular sources. An attempt is made to discuss the methods of the subject systematically.