LaTeX.org

first of all, thank you so much for your kind suggestion and warm welcome

well, first of all I examined the personal packages that I was loading in my document

(where personal means: composed of personal original macros)

and I found out that one of the macros introduced by my coauthor was

\def ...

the command for double acute accent, say over the ``o'' (Hungarian accent) is

\H{o}

but for some strange reason when I use it in my document (book document class) this command produces

Ho

I guess the reason may be that there is a conflict with one of the packages that I have loaded for my ...