Comment on ‘Sky analysis from CCD images: cloud cover’ by G Roy,S Hayman and W Julian

Abbott PF . Guidelines on the Quality Control of Surface Climatological Data. World Climate Research Program WMO/TD Publication No 111 World Meteorological Organisation 1986.

Galligan AM. Variability of subjective cloud observations. Technical Report AFCRC 53-10 Air Force Cambridge Research Center, Cambridge MA, 1953.