You are downloading the MathRef XAP file v18.104.22.168 for Windows Phone. MathRef is a free and useful Productivity app: This app gives you just a sample over 1,400 helpful formulas, figures, tips, and examples. Math Ref is just an awesomely useful app for ... You can now download the offline XAP file to install & try it.
Download Locations for MathRef 22.214.171.124 XAP file
Note: To install it manually from an SD card, you should choose one of the server location above to get the offline MathRef XAP file, move the file to your phone's SD card and then tap 'Install local apps' in the phone's App list.