Graph partitioning with parts of equal size Partition an undirected graph of $n$ nodes into $k$ subgraphs so that total vertices inside all subgraphs is maximum.
Restriction: all subgraphs have the same number of nodes (so $k$ divides $n$); $k$ is given initially.

I'd like to receive pointers to the solution as well as papers or blogs related to or expanding on it.
Your problem is a special case of graph partitioning. When $k=2$, the problem is known as minimum bisection, and is NP-complete.