prov:value
| - The invention relates most especially to compounds of formula Ia in which R1 is C1 -C4 alkyl, such as methyl, R2 is C1 -C4 alkyl, such as propyl, X is oxy, alk is C2 -C5 alkylene, such as ethylene, 1,3-propylene or 1,4-butylene, n is 2, R3 is 3-thienyl or 3-furyl each of which is unsubstituted or is mono- or di-substituted, especially in the 2- and/or 5- position, by halogen having an atomic numbe
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