Text ( visual ) : unmediated URSI handbook of ionogram interpretation and reduction of the World Wide Soundings Committee / edited by W. R. Piggott and K. Rawer. -- Amsterdam : Elsevier ; Van Noastrand , 1961. -- xi, 192 p. : ill. ; 24 cm. -- (URSI monographs). -- (BA43461053) ; https://ci.nii.ac.jp/ncid/BA43461053 Author Heading(s): International Scientific Radio Union. World Wide Soundings Committee ; Piggott, W. R. ; Rawer, K. (Karl). -- Classification(s): DC18 : 551.5145