Keywords: Mittelholzer-tschadsee.jpg Lake Chad in December 1930 Air photo taken by Swiss pilot and photographer Walter Mittelholzer 1894-1937 Own scan from book Tschadseeflug by Walter Mittelholzer published in 1932 in Switzerland publisher Verlag Schweizer Aero-Revue in Zürich 1930-12 creation 1932 publication Walter Mittelholzer 1894-1937 Walter Mittelholzer PD-old Swiss copyright on Mittelholzer's work's expired at the end of 1987 since Switzerland had a copyright term of 50 years p m a until 1993 and the extension to 70 years p m a made in 1993 did not restore already expired copyrights Lake Chad Aerial photographs of Chad |