a compound having an active hydrogen and {HEAD ~ an acid group}, said {TAIL ~ compound} being selected from the group consisting of salicylic acid, thiosalicylic acid, p hydroxybenzoic acid, 3,5 dihydroxybenzoic acid, p aminobenzoic acid, anthranilic acid, and p hydroxyphenylacetic acid, 
a compound having an active hydrogen and { HEAD ~ an acid group } , said { TAIL ~ compound } being selected from the group consisting of salicylic acid , thiosalicylic acid , p hydroxybenzoic acid , 3,5 dihydroxybenzoic acid , p aminobenzoic acid , anthranilic acid , and p hydroxyphenylacetic acid ,
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH