"Lucid program design: the grammar of OPAQUE," Tech. Memo No. TM-1749/301/O0 (Vol 3 of report)

SYSTEM DEVELOPMENT CORP., (1964) SYSTEM DEVELOPMENT CORP., "System design specifications for LUCID phase I," Tech. Memo No. TM-1749/0O0/O0, Santa Monica, Calif., Jan. 1964.  

Languages mentioned LUCID {1964} Data query language