Select query help

I have tblLog. It's fields a
Call: text
Freq: single
Mode: text
CID: text
QSL_R: text
Credited: T/F

I need the SQL to return all records where 'Credited' is false, 'QSL_R' NULL or
blank, and whose combination of 'Freq' and 'Mode' for a given 'CID' have 'Credited' =
false, but not if that record has a 'mate' whose 'CID', 'Freq/Mode', 'QSL_R' all
match, and 'Credited' is True.

I'm not sure if my description is understandable, so here is an example.

Call Freq Mode CID QSL_R Credited
1A0KK 14.210 SSB 1A0 Y True
1A0XX 14.210 SSB 1A0 Y False
1A0LY 14.310 CW 1A0 Y False
1A0KK 7.009 CW 1A0 Y True
1A0TT 3.506 TTY 1A0 False
NF4L 18.080 TTY K Y False
NF1Y 18.083 TTY K False
WA4B 7.080 TTY K Y True
K4UTE 18.125 SSB K Y False
AB4UF 14.230 SSB K Y False

These records should be in the return set.
1A0LY 14.310 CW 1A0 Y False
NF4L 18.080 TTY K Y False
K4UTE 18.125 SSB K Y False
AB4UF 14.230 SSB K Y False

Thanks,
Mike