an official letter的用法和樣例：
例句
- She received several official letters this morning.
她今天早晨收到了幾封公函。 - For this reason, it is improper for a notarial agency to directly issue an official letter or allow notaries make a video telephone attestation at the request of a foreign court.
因此，公證處不宜應外國法院要求直接出具公函并由公證員在可視電話(huà)上作證。
