Vanderbeek, Greg. Order of Operations and RPN (Expository paper). Master of Arts in Teaching (MAT) Exam Expository Papers. Lincoln, Nebraska, USA: University of Nebraska. June 2007 [2020-06-14]. Paper 46. (原始内容存档于2020-06-14).
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Ask Dr. Math. Math Forum. 2000-11-22 [2012-03-05]. (原始内容存档于2021-04-21).
Vanderbeek, Greg. Order of Operations and RPN (Expository paper). Master of Arts in Teaching (MAT) Exam Expository Papers. Lincoln, Nebraska, USA: University of Nebraska. June 2007 [2020-06-14]. Paper 46. (原始内容存档于2020-06-14).
Order of operations(DOC). Syllabus.bos.nsw.edu.au. [2019-08-02]. (原始内容存档于2021-02-24).