Sources are not about a topic they are about where the information came from. Every thing in that paragraph is from the source cited. There is no reason to affix another source or add multiple listings of the same source, as no other source has been introduced. The topic may have changed, the source did not. If you want to find additional sources, feel free to look. Articles can always use improvement. I have been instructed by numerous administrators NOT to cite sources on a list of published works. They are "published", thus people can find them. If you google him, the very first thing that comes up after his wiki page is a link to his books.