It appears you don't have a PDF plugin for this browser. You can click here to download the reference manual.
1.1.3 by Randy Lai, 4 years ago
https://randy3k.github.io/xptr/
Browse source code at https://github.com/cran/xptr
Authors: Randy Lai [aut, cre]
Documentation: PDF Manual
MIT + file LICENSE license
See at CRAN