at stated intervals

at sale at sb's back at sb's beck and call at sb's bidding at sb's disposal at sb's disposition at sb's expense at sb's feet at sb's insistence at sb's insistent request at sb's service at sb's suggestion

dihydrocoumarin dihydrocuminaldehyde dihydrocyciocitral dihydrodaunomycin dihydrodeoxystreptomycin dihydrodesoxycodeine dihydrodesoxymorphine dihydrodesoxymorphine-D dihydrodiethylstilbestrol dihydrodiketoanthracene