Many items which are collections of primary source material have sources as part of their headings. Another useful technique is to perform a search for your topic and then limit the resullting set of records to items published during the time period in question. This technique is also very helpful for periodical indexes such as PCI which cover a wide span of years. Once you have retrieved a few relevant bibliographic records, you may use the hotlinked subject headings to locate additional relevant materials. Typesetting itself changes a document.
Facsimiles preserve the original but someone still has to chose which texts to copy.
There s nothing like getting your hands on original undisturbed ditems. For instance, the order in which an author or organization kept their documents may be indicative of something significant. In theory, most anything could be a primary source. The following sources reflect the viewpoints and attitudes of their times. Sometimes differentiating among primary sources is tricky, e.g. eyewitnesses.