1. Comparison of the Ångström Pyrheliometer and the Callendar Sunshine Recorder;Patterson,1912
2. The Silver-Disk Pyrheliometer;Abbot;Smithsonian Miscellaneous Collections,1922
3. On Pyrheliometric Measurements;Ångström;Tellus,1958
4. Absolutpyrheliometer-Vergleichungen Davos 1930–1946;Courvoisier,1954
5. Pyrheliometric Calibration Program of the U. S. Weather Bureau;MacDonald;Monthly Weather Review,1954