source <a href=httpsarchiveorgdetailsjournalofsociety18socirichpagen145mode2up>Journal of the Society of Motion Picture Engineers<a> February 1932 p141<br>Frederick 氏の縦溝レコード論文のアブストラクト<br>Abstract section of HA Fredericks Vertical record paper
“Vertical Sound Records” (Frederick, JSPTE, 1932)