I use many self-made libraries for many of my OpenSCAD projects. If you compile one of my scads and it says "file not found", good odds it's looking for one of these.
Also found here are explanations for math too complicated to elegantly display in a computer language, and references I don't want to lose.
Name Last modified Size DescriptionApache Server at burningsmell.org Port 80
Parent Directory - util.scad 12-Sep-2017 19:53 8.8K Tons of little time-saving one-shots. Latest version. util-0.1.1.scad 12-Sep-2017 19:53 8.8K Now with support() module vitamins/ 17-Jul-2017 19:58 - dimensions/ 14-Jul-2017 17:25 - Measurements and Tables util-0.1.0.scad 12-Jul-2017 17:53 7.6K Gerotor_Modeling_with_NX3.pdf 09-Jan-2017 22:15 1.2M Magic formula for making gerotors tsmthread.scad 09-Jan-2017 22:11 2.3K Fast OpenSCAD Thread Generator util-0.0.1.scad 09-Jan-2017 19:28 6.2K Old lib for pre-2016 OpenSCAD