Sánchez, Robert. "The Border Crosser or Commuter Problem: New Developments." N.p. [typescript], undated

Sánchez, Robert. "The Border Crosser or Commuter Problem: New Developments." N.p. [typescript], undated, Box: 196, Folder: 17. Julian Samora Papers, 24426265. Benson Latin American Collection, The University of Texas at Austin. https://archives.lib.utexas.edu/repositories/4/archival_objects/389739 Accessed September 27, 2026.