https://www.particleincell.com/2012/curvilinear-coordinates/
Orthogonal Curvilinear Coordinates
Cylindrical and spherical coordinates are just two examples of general orthogonal curvilinear coordinates. In this article we derive the vector operators such...
curvilinear coordinatesorthogonal
https://books.physics.oregonstate.edu/GVC/coords.html
Curvilinear Coordinates
curvilinear coordinates