Primary source: arxiv.org/abs/1603.02720
Verified locator: Primary author preprint, exact byline Steven J. Byrnes. arXiv 1603.02720, initially submitted 6 March 2016; version 5 revised 30 December 2020. §4.1 defines interface forward/backward amplitudes and layer propagation; Appendix A explains reflection-amplitude sign conventions. Full text: arxiv.org/html/1603.02720v5 . The HTML-generated title-page date is not treated as the original submission date.