Yes, the NASA stuff is good practical advice.
But, I still need a reference for a statement like
My understanding be that known icing = in cloud above the zero level
Physically speaking, it isn't
known icing, because as any pilot will tell you, most of the time you won't pick up any ice at all. Today I spent nearly 2 hrs in IMC at below 0C and picked up a total of about 2mm of rime, in all that time. No measurable loss of IAS.
OTOH, looking at e.g.
http://ows.public.sembach.af.mil/
(Flight Hazards -> Icing)
you get what might be a plausible map of where you might get some real ice.