Historians distinguish between primary and secondary or even ternary sources. A primary source for, say, a biography would be a birth or death record, personal letters, handwritten drafts of papers by the subject of the biography, or even a published paper by the subject. A secondary source could be a biography written by someone who had examined the primary sources, or a non-photographic copy of a primary source. Ternary sources are things pieced together from secondary sources—encyclopædia or other survey articles, term papers, etc.1 The historian's preference is for primary sources. The further removed from the primary, the less reliable the source: errors are made and propagated in copying; editing and summarising can omit relevant details, and replace facts by interpretations; and speculation becomes established fact even though there is no evidence supporting the “fact”.2
KeywordsGeometric Algebra Elementary Mathematic Annotate Bibliography Source Book Pythagorean Theorem
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