Complex sentence: The max-cut problem is one of Karp's 21 NP-complete problems; the proof comes by transformation from maximum 2-satisfiability (a restriction of the maximum satisfiability problem).
Split into simpler sentences: The max-cut problem is one of Karp's 21 NP-complete problems. The proof of max-cut problem's NP-completeness comes by transformation from maximum 2-satisfiability (a restriction of the maximum satisfiability problem).