| http://www.w3.org/ns/prov#value | - A nitrogen containing heterocyclic compound as claimed in claim 1 wherein one of R.sub.1 and R.sub.2 is a member selected from the group consisting of a lower alkyl group, a phenyl group, a halophenyl group, and a lower alkoxyphenyl group andthe other of them is a hydrogen atom or a lower alkyl group; R.sub.3 is a hydrogen atom; X is an imino group, or ##STR160## wherein R.sub.4' is a member selec
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