Complexity and Stop Conditions for NP as General Assignment Problems,   the Travel Salesman Problem in $\mathbb{R}^2$, Knight Tour Problem and   Boolean Satisfiability Problem
  This paper presents stop conditions for solving General Assignment Problems (GAP), in particular for Travel Salesman Problem in an Euclidian 2D space the well known condition Jordan's simple curve and opposite condition for the Knight Tour Problem. The Jordan's simple curve condition means that a optimal trajectory must be simple curve, i.e., without crossing but for Knight Tour Problem we use the contrary, the feasible trajectory must have crossing in all cities of the tour. The paper presents the algorithms, examples and some results come from Concorde's Home page. Several problem are studied to depict their properties. A classical decision problem SAT is studied in detail. 
Carlos Barr\'on-Romero
cs.DS