He also developed a multilevel reading program for students beyond the primary level, including adults, who performed lower than others (Corrective Reading Decoding and Corrective Reading Comprehension), programs to teach writing and spelling (Reasoning and Writing and Spelling Mastery), and a videodisk series to teach math and science to middle school students (including Chemistry and Energy and Elementary Earth Science).
Siegfried Line | Siegfried & Roy | Siegfried | Siegfried (opera) | Siegfried Wagner | Siegfried Matthus | Siegfried Lenz | Siegfried Palm | Siegfried II of Westerburg | George Engelmann | Siegfried von Feuchtwangen | Siegfried Kasche | Siegfried, Count of Merseburg | Siegfried Bernfeld | ''Siegfried'' | Chris Siegfried | Bernhard Siegfried Albinus | Wolf pack Siegfried | Siegfried Verbeke | Siegfried Tiefensee | Siegfried Strelow | Siegfried Selberherr | Siegfried Saloman | Siegfried Reiprich | Siegfried of Luxembourg | Siegfried of Isenburg-Kempenich | ''Siegfried Map'' of the Türlersee | Siegfried Lenz. | Siegfried Köhler | Siegfried III |