“Single Window is defined as a facility that allows parties involved in trade and transport to lodge standardized information and documents with a single entry point to fulfil all import, export, and transit-related regulatory requirements”
UN/CEFACT RECOMMENDATION No. 33
Full text of the article: http://www.tfafacility.org/sites/default/files/case-studies/the_long_and_winding_road_how_wto_members_finally_reached_a_tfa_e.pdf