CGTrader - CGTrader is an online marketplace at which artists can sell and buy Revit and 3D models.
PhotoStudy - Stuck on a Math or Science Problem? Get Help From an Expert Tutor in Seconds!
3DExport - 3DExport is a 3D model marketplace where you can buy and sell 3D models, CG textures and digital objects for 3D printing with royalty free. Professional 3D models - 3DExport.com
Math.com - Math.
TurboSquid - TurboSquid offers 3D models for professionals.
Mathway - Mathway is a freemium math solving app that helps you find the solutions to any math problem you can imagine.