L SDA_EXTENSIONS_DOC, Programming, A manual for writing SDA callout extensions  A SDA_EXTENSIONS_DOC -- A manual for writing SDA callout extensions @ Written by Ing. Ferry Bolhr-Nordenkampf <bol@adv.magwien.gv.at>  I (Presented in DECdocument source, text, Bookreader, HTML, and PostScript)     