We are not allowed to link tem on here as Niantic do not confirm the grid based rulings, they are player observations.
Do a search for Wayfarer Tools, there is also a Discord server you can join if you need help.
And just to add a Notice I add to most of these post. Never use knowledge of the cell system to misplace waypoints to get them in the game. This can lead to suspensions on wayfarer and game accounts.
They can be used to see what may become a stop / gym or even what will become a dynamax powerspot.
They can also be used to make a decision when a waypoint as more than one correct location. Example: Football Field. Place behind goal. Cells can help decide which goal…