"Material that supplements the content of the paper, but would be distracting or inappropriate to include in the body of the paper is to be placed in an appendix." This includes "materials that are relatively brief and that are easily presented in print format" (Publication Manual of the APA: 6th edition, section 2.13; Publication Manual of the APA: 7th edition, section 2.14). Examples include "mathematical proofs, lists of words, a questionnaire used in the research, a detailed description of an apparatus used in the research, etc" (Purdue OWL.)
An appendix (or appendices) follow the reference list. Use the following order for your paper:
"produced the same results for both studies (see Appendices A and B for complete proofs)."
A sample appendix is below:
