Timo Niemi, Kalervo Järvelin Operation-oriented query language approach for recursive queries - Part 1. Functional definition. [Citation Graph (0, 0)][DBLP] Inf. Syst., 1992, v:17, n:1, pp:49-75 [Journal]
Timo Niemi, Kalervo Järvelin Operation-oriented query language approach for recursive queries - Part 2. Prototype implementation and its integration with relational databases. [Citation Graph (0, 0)][DBLP] Inf. Syst., 1992, v:17, n:1, pp:77-106 [Journal]