Barron, C. Housel , Nan C. Shu "A high-level data manipulation language for hierarchical data structures" pp155-169

[SIGPLAN] (1976) SIGPLAN Notices 11(02) February 1976 also Proceedings of the SIGPLAN '76 Conference on Data: Abstraction, Definition and Structure, Salt Lake City, Utah, USA, March 22-24, 1976  

Languages mentioned BOLTS {1974} CONVERT {1976} HQL {1974} SEQUEL {1973} Limited expression language for data querying