The Synthesis of Stable 8-Alkylidene-9H-pyrazolo[4,3-d]tetrazolo [1,5-b]pyridazine Azomethine Imines and Their Transformation into 9,10-Dihydro-8H-tetrazolo[1',5' :1,6]-pyridazino [4,5-c] [1,2] diazepines, Derivatives of a Novel Heterocyclic System - Žličar, Marko; Huč, Branko; Stanovnik, Branko; Tišler, Miha (Synlett, 1990)