Perturbation Series in Light-Cone Diagrams of Green Function of String   Field
  In this paper, we proved the correspondence between Feynman diagrams in space-time and light-cone diagrams in world-sheet by using only path integral representation on free Green function in the first quantization theory. We also obtained general representation on perturbation series of light-cone diagrams describing split and join of strings. 
Am-Gil Li, Tae-Song Kim, Chol-Man Li, Song-Jin Im
physics.gen-ph hep-th