Thank you very much
momoha!!! Your code does work!!!

The properties involved are very complex and I didn't know many of them. So, many thanks again.
Rubén
EDIT: Your styles also work in <p> tags, so if I add the properties you indicated me in
and nothing in <body> it also works!!

By chance, do you have something to handle "breaks" after some tags? Because "page-break-after: avoid" (or "break-after: avoid") under epub3 with ADE doesn't work. Hopefully you have something for that too