1. MTA-ELTE Matroid Optimization Research Group, ELKH-ELTE Egerváry Research Group, Department of Operations Research, Eötvös Loránd University, Budapest, Hungary.
2. Alfréd Rényi Institute of Mathematics and ELKH-ELTE Egerváry Research Group, Department of Operations Research, Eötvös Loránd University, Budapest, Hungary.
3. MTA-ELTE Matroid Optimization Research Group, Department of Operations Research, Eötvös Loránd University, Budapest, Hungary.