In every sentence in which the so-called subject marker `-에서` occurs, the hidden subject can be found out by three syntactic features of Korean subjects as follows. Korean plural marker `-들` pluralize the subject when it is used after any constituent which cannot be pluralized. Then `-들` can pluralize something in this way in the sentence with `-에서`. even though the NP before `-에서` is still singular. So we can say that there must be a hidden subject in it. Although inanimate subject cannot co-occur with honorific expression `-시-` and the NP before `-에서` is inanimate, `-시-` can be used in the predicate of the sentence with `-에서`. This means that there must be a hidden subject in the sentence again. The 3rd person reflexive pronoun `자기` is used to co-refer someone with the subject in a sentence. Then in the very sentence with `-에서`, `자기` can occur. But the NP before `-에서` cannot be a human. So there must be a hidden subject which co-refers someone with `자기`.