Welcome to the site! It's always neat to learn what other countries call other things/parts of a car.
Here in the states we call the rear windows in a coupe the "quarter glass". We call what you're referring to either a "wing window" or "vent window." We even have different names for it in the states!
The post above should be what you're looking for. If not, if you're trying to actually remove it from the door, you pretty much have to gut the door. It's easier to get out if you remove the inside door regulator, the window (you can remove the rear channel - feel and look for the screws, remove the regulator, and let the glass/regulator sit in the bottom of the door) then remove the 3 or 4 screws along the leading edge of the door that screw into the vent window, then there's two screws at the bottom. Tilt it back, pull it most of the way out, then it needs to be rotated 90* to get it out the rest of the way. It's quite a task, but not hard.
Check out this video:
and this one (wrong year truck 73-87 but very similar):
Attached is what we call the quarter glass
