1. American Institute of Certified Public Accountants 2015 The Uni-form CPA Examination: Purpose and structure http://www.aicpa.org/BecomeACPA/CPAExam/ExamOverview/PurposeandStructure/Pages/default.aspx
2. American Academy of Physician Assistants 2015 https://www.aapa.org/Become-a-PA/
3. Graphs in statistical analysis;Anscombe;American Statistician,1973
4. Some experimental results in the correlation of mental abilities;Brown;British Journal of Psychology,1910