"The Lower ionosphere. "; "Friend, A. W.", "Colwell, R. C."; "Ionosphere."; "Colwell, R. C.", "Friend, A. W."; "1936"; "Journal article reprint from: The Physical Review, v.50:no.7 (1936:Oct. 1). "; ""; "P1225"; "pec"; "Ionosphere."; "14256"; .