On the Topological Term in the String Representation of the Wilson Loop   in the Dilute Instanton Gas
  A topological term related to the number of self-intersections of the string world-sheet is shown to emerge in the string representation of the Wilson loop in the dilute instanton gas. The coupling constant of this term occurs to be proportional to the topological charge of the instanton gas under consideration. 
D.V.Antonov (Humboldt University, Berlin and ITEP, Moscow) and D.Ebert   (Humboldt University, Berlin)