Hello, I am trying to find a thorough documentation for the SDF elements, so I can completely understand how to use them inside the SDF file for my model that I want to load in the Gazebosim environment. sdfformat.org is not enough for me. I have once stumbled upon a website that provided extensive information about the SDF elements (describing all the physical properties needed for a joint in Gazebo simulation environment and providing explanation about the code implementation to achieve such desired properties), but i am not currently able to find the site, so if you can help me with anything it would be much appreciated. Thank you!