[Athena21]

Again, thank you so much for your help.

I have 2 more questions.

1) Do you know of a good English grammar book? I think it would help me greatly.

2) Another grammar question:

Is it ok to say: I heard a ringing phone.

I'm pretty sure it is ok but I can't remember the rule. I know that "a" implies I don't know what phone is ringing, I just hear a phone ringing. But is it ok to just say this sentence without adding anything else?