Adam Smith's use of multiple references for his pin making example

At the beginning of The Wealth of Nations Adam Smith describes a pin factory. It is widely accepted that this example comes from Diderot's Encyclopaedia, published in France in the 18th century. The details in the text together with the conferences previously given in Glasgow clearly show that this one reference cannot be the only source. Three other French publications on pin making may also have been used as references for Adam Smith's text. Phrase by phrase these texts are compared to Smith's to support the assertion that he based his work on four previous French publications. The Wealth of Nations unites and synthesizes these different sources and excerpts those parts that confirm his theory. Smith should have listed his sources.