請問Cornell推薦信翻譯的問題

[scudder]

Non-native English speaking evaluators who choose to write the letter in
their native language and then have it translated into English must use this
option. In these cases, evaluators must submit a signed evaluation written in
the native language along with the official translation also signed by the
evaluator.

這段是說推薦人不是用英文寫 一定要請人翻譯並簽名
但official translation是指公證人簽名 或經過公證嗎?
可以由推薦人所認識的會英文的同事簽名嗎?
謝謝指點~