The revised, corrected and improved edition of the book by Peet Johnson is now available. I have actually had a small hand in things this time. This new revised edition is most highly commended. The book can be ordered here.
Looking at the music of Dutch rock band Focus, started in the late sixties by Thijs Van Leer (b /31/03/48) with Jan Akkerman (b 24/12/46). Van Leer still performs and records under the name today (official site here). Akkerman's site here.