References
- Brooks , C. E.P. 1970 . Climate Through the Ages , Dover Publications .
- Flohn , Herman . 1969 . Climate and Weather , McGraw-Hill .
- 1975 . Hydrograph of Monthly Mean Levels of the Great Lakes , National Ocean Survey, NOAA, U.S. Department of Commerce .
- Powers and Witt . 1972 . Travelling Weatherwise in the U.S.A. Dodd, Mead
- Silverberg , Robert . 1969 . The Challenge of Climate , Meredith Press .
- Sky and Telescope magazine Jan. 1974-Jan. 1976 (Sunspot numbers)
- Stetson , Harlan T. 1947 . Sunspots in Action , The Ronald Press Co. .
- Weather data from the Climatological Records of the U.S. Department of Commerce, National Climatic Center, Asheville, N.C.
- 1974 . Yearbook of Science and Technology , McGraw-Hill .