Subject: chapter headers on pages
Hi: It used to be that DocBooks that I rendered to PDF would have the chapter title at the top of each page. Recently it has disappeared: I only see the separation line at the top. Either there is a problem with page size (so that it falls out of boundaries) or with the style sheets. I did not change my mark-up nor style sheets; I supposed the standard style sheets have changed. How do I get header titles back?