Sentence:  Other sources of information include the <WSD>National</WSD> Concrete Masonry Association , 38 South Dearborn Street , Chicago , Ill. , the Portland Cement Association , 33 West Grand Avenue , Chicago , Ill. , and the Structural Clay Products Association , Washington , D. C. . 
Meaning of the word marked with <WSD> tags:  any number of entities (members) considered as a unit