It's in 61.58. You have to pass a checkride in a multicrew or turbojet plane every year and you have to pass a checkride in the airplane you want to stay current in every two years. And the checkride has to be given by someone authorized by the FAA. If it's a biz jet the training center in Europe may be on the FAA list. If you're flying an airliner, I don't recall any European airlines running FAA training.