Source : Free On-Line Dictionary of Computing

L6
     
        Bell Telephone Laboratories Low-Level Linked List Language.
        Ken Knowlton, 1965.  List processing language, typeless.
     
        ["A Programmer's Description of L6, Bell Telephone
        Laboratories' Low-Level Linked List Language", K. Knowlton
        CACM 9(8):616-625 (Aug 1966).  Sammet 1969, pp.400- 405].