1. The C programming language;Kernigham,1978
2. La balance de Godhavn;La Cour;Danish Meteorological Institute, Comunications Magnétiques no. 8,1930
3. Le variomètre de Copenhague;La Cour;Danish Meteorological Institute, Comunications Magnétiques no. 11,1930
4. On the scale value and the base value of the H-variometer;Ryd;Danish Meteorological Institute, Comunications Magnétiques no. 12,1930
5. Notes on geomagnetic observatory and survey practice;Wienert,1970