1. Admiralty Hydrographic Department 1938 In Admiralty weather manual, pp. 28–29. HMSO, London
2. Air Ministry 1936 In Marine observers' handbook, p. 38. Meteorological Office, London
3. 1904 Recherches oceanographiques: expedition de M. A-G. Nathorst en 1899. Matematik och Naturvetenskap. 1. Berling. Uppsala Universitets Arsskrift.
4. 1917 In A manual of marine meteorology for apprentices and officers of the world's merchant navies, pp. 17–18, 2nd Edition. Charles Griffin, London