Sentence:  Historically, target words were garnered through focused reading programs and <WSD>citations</WSD> were handwritten on slips of paper which were collated alphabetically and stored in drawers for ready access (much like old-fashioned library catalogues). 
Meaning of the word marked with <WSD> tags:  A quotation with attached bibliographical details demonstrating the use of a particular lexical item in a dictionary, especially a dictionary on historical principles.