1. Project Blue Book, ed. Brad Steiger, Ballantine Books, 1976
    2 Report on Planet Three, Arthur C. Clarke
    3 Man and the Stars, Duncan Lunan, Souvenir Press, 1974
    4 UFOS - Identified, Philip J. Klass, Random House, 1968
    5 Klass appears to have changed his mind about this after 1968, and later believed that all UFOs had 'prosaic' explanations.
    6 The UFO Handbook, Allan Hendry, Doubleday, 1979
    7 Hendry
    8 Unsolved Mysteries of the Arctic, Vilhjalmur Stefansson, Collier Books, 1962
    9 Nature, 1506, 58, p.460, 1898
    10 Andrée's fate was unknown until 1930, when his remains were discovered on White Island, 250 miles east of Spitzbergen.
    11 The Report on Unidentified Flying Objects, Edward J. Ruppelt, Gollancz, 1956
    12 Spyplane, Norman Polmar, MBI, 2001
    13 R. P. Greg, ‘Catalogue of Meteors & Fireballs from AD 2 to AD 1860’. Report of the British Association, 1860, p. 62.
    14 Neil Charman, 'Ball lightning photographed?' New Scientist, 26 February 1976
    15 Charman
    16 Journal of Meteorology, 1:10
    17 Journal of Meteorology, 1:10
    18 Weather, 4,31,1976
    19 Journal of Meteorology, 8:82
    20 Weather, 37:3
    21 Stow's Annals, Journal of Meteorology, 1:10
    22 Journal of Meteorology, 9:94
    23 Rev. F. J. Clayton, The Times, 1936
    24 Meteorological Magazine, 903:76, Sept. 1947
    25 Charman
    26 Challenge to Science - the UFO Enigma, Jacques & Janine Vallee, Tandem Books, 1974
    27 The UFO Experience, J. Allen Hynek,
    28 UFOs from behind the Iron Curtain, Ion Hobana & Julien Neverbergh, Souvenir Press, 1974
    29 The Hynek UFO Report, J. Allen Hynek, Sphere Books, 1978
    30 Vallee
    31 Remarkable Luminous Phenomena in Nature, William R. Corliss, Sourcebook Project, 2001
    32 National Investigation Committee on Aerial Phenomena (USA)
    33 Hobana & Neverbergh
    34 The Hynek UFO Report
    35 Messengers of Deception, Jacques Vallee, And/Or Press, 1979
    36 Messengers of Deception
    37 Messengers of Deception
    38 UFOs & the Limits of Science, Ronald D. Story, New English Library, 1981
    39 Hendry
    40 Challenge to Science - the UFO Enigma
    41 Shambhala: In search of the new era, Nicholas Roerich, Rochester, VE: Inner Traditions, 1990 (1930)
    42 Messengers of Deception
    43 Hobana & Neverbergh
    44 The Encyclopaedia of UFOs, Ronald D. Storey, ed. New English Library,1980
    45 UFOS - Identified
    46 Journal of Meteorology, 3:26
    47 Hobana & Neverbergh
    48 Lightning, Auroras, Nocturnal Lights & related luminous phenomena. William R. Corliss, Sourcebook Project, 1982
    49 ‘Observations of Luminous Meteors’, 23rd Report of the B.A.A.S., 1853
    50 ‘3rd Report on the facts of Earthquake Phenomena’, Robert Mallet, B.A.A.S. Report, 1852
    51 Challenge to Science - the UFO Enigma
    52 The Evidence for UFOs. Hilary Evans
    53 Phenomena, John Michell & Robert J.M. Rickard, Thames & Hudson, 1977
    54 Challenge to Science - the UFO Enigma
    55 The Truth about Flying Saucers, Aimé Michel, Robert Hale, 1957
    56 Anatomy of a Phenomenon, Jacques & Janine Vallee, Tandem Books, 1974
    57 Handbook of Unusual Natural Phenomena, William R. Corliss, Sourcebook Project, 1977
    58 'Luminous Phenomena in Nocturnal Tornadoes', B. Vonnegut & J. R. Weyer, Science, vol. 153, Sept. 1966
    59 'Dehydration and Burning Produced by the Tornado', P. A. Silberg, Journal of the Atmospheric Sciences, vol.23, March 1966
    60 Tornadoes, Dark Days, Anomalous Precipitation & related weather phenomena. William R. Corliss, Sourcebook Project, 1983
61 The Nature of Ball Lightning. Stanley Singer. Plenum Press, 1971
62 Daily Mirror, 10 July 1967
63 Flying Saucers on the Moon. H. T. Wilkins, Peter Owen Ltd., 1954
64 UFO Photographs Around the World, vol. 1. W. C. Stevens & A. C. Roberts. UFO Photo Archives, 1986