I have used the notation that all forex pairs Ric codes not containing USD end up with = sign .
eg:
EURGBP=
AUDCAD= etc..
However I found that the following instruments do not exist when I add = as a postfix
GBPSGD=
NZDCAD=
NZDSGD=
NZDCHF=
Can anyone explain how do I find the above instruments?