If you’re using someone else’s work, quoting or paraphrasing someone, or making a bold or controversial statement attributed to someone else, always cite your source. Whether the material is copyrighted or not, whether it falls under ‘fair use’ or not, always cite your source.

On the one hand, many entities, e.g. archives, require a specific citation when using their material that they will provide you; on the other, it is etiquette and a professional courtesy to cite the source. However, yo...