conf/sigmod/76 Claude Deheneffe Henri Hennebert NUL: A Navigational User's Language for a Network Structured Data Base. 135-142 1976 SIGMOD Conference db/conf/sigmod/sigmod76.html#DeheneffeH76 http://doi.acm.org/10.1145/509383.509402 db/conf/sigmod/DeheneffeH76.html SIGMOD76/P135.PDF ... ... conf/ifip/DeheneffeHP74 conf/ifip/HainautL74 journals/tods/Chen76 journals/cacm/Bachman73 ... journals/cacm/Codd70 conf/sigmod/ChamberlinB74 journals/cacm/BoyceCKH75 ...