| prov:value
| - A compound of the formula ##STR29## wherein X1 is (C(R1)2)n where R1 is independently H or alkyl of 1 to 6 carbons, and n is an integer between 0 and 2;X2 is S or O; Z is --(CR1 ???CR1)n,-- where n' is an integer having the value 0-2,--COO--, --OCO--; --CSO--; --OCS--; --CO--CR1 ???CR1 --; R2 is hydrogen, lower alkyl of 1 to 6 carbons, F, Cl, Br, I, CF3, fluoro substituted alkyl of 1 to 6 carbons,
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