In my 28 April reply to David Mullens about suggested grammars for continued
study and use of NT Greek, I forgot to mention two books designed to help us
keep up the use of Greek: Neal Windham's 1991 "New Testament Greek for
Preachers and Teachers: Five Areas of Application" from University Press of
America, and David Alan Black's 1993 "Using New Testament Greek in Ministry"
from--I think--Baker. Both books have helpful bibliography lists.
Countryman's strangely titled "The New Testament is in Greek" has a useful
list of books to choose for further study as well.