And an interesting page of a book about Zworykin  httpbooksgooglecombooksidtyurXyEBPxkCpgPAlpgPAdqtihanyisourceblotsbsqrzBQAsigJAdSPIxpRCNlggCGSyGgIsghlhueifpbSsFIYKDQaviCCwsaXoibookresultctresultresnum