prov:value
| - t at least one of A1 -B1, B1 -C1, C1 -D1, A2 -B2, B2 -C2, C2 -D2, A3 -B3, B3 -C3, C3 -D3, A4 -B4, B4 -C4, and C4 -D4 combinations may combine to form a benzene ring; R1, R2, R3 and R4 each is an alkyl or aryl group; R5 and R6 each is a lower alkyl group; L1, L2 and L3 each is a methine group; X.sup.??? represents an acidic ion; n1 is 1 or 2; and l1 is zero or 1, provided that when the compound for
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