Reference for Gittin 38:13

אמר שמואל נתן לה נייר חלק ואמר לה ה"ז גיטיך מגורשת חיישינן שמא במי מילין כתבו

or written in Greek and signed in Hebrew, it is valid. — If I had only that to go by, I should say that this is the case only with writs of divorce, but not with other documents. Now I know [that this applies to other documents also].

Jastrow