For example Leo Deuel - Flights into yesterday: the story of aerial archeology, St. Martin's Press, 1969, ISBN 9780356031521, p. 38: "In this way, vegetation acts in somewhat the manner of a chemical developer of exposed photographic plates: it throws up the latent pictures." Author likely to use a quote of some pioneer in this field, perhaps even Crawford himself.
Kwa mfano Leo Deuel - Flights ndani ya jana: hadithi ya akiolojia angani, Press St Martin, 1969, ISBN 9780356031521, p. 38: "Kwa njia hii, uoto wa vitendo kwa namna fulani ya kemikali developer ya sahani za picha wazi: ni throws up picha latent." Author uwezekano wa kutumia quote wa waanzilishi wengine katika uwanja huu, pengine hata Crawford mwenyewe.