I have a minimal example here that creates lowercase headings.
\documentclass[12pt, a4paper, oneside, onecolumn]{book}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[ngerman]{babel}
\usepackage[round]{natbib}
\usepackage{lipsum, filecontents}
\usepackage{fancyhdr}
\pagestyle{fancy}
\renewcommand{\chaptermark}[1]{%
\markboth{#1}{}}
\renewcommand{\sectionmark}[1]{%
\markright{\thesection\ #1}}
\fancyhf{} % delete current header and footer
\fancyhead[LE,RO]{\bfseries\thepage}
\fancyhead[LO]{\bfseries\rightmark}
\fancyhead[RE]{\bfseries\leftmark}
\renewcommand{\headrulewidth}{0.5pt}
\renewcommand{\footrulewidth}{0pt}
\addtolength{\headheight}{0.5pt} % space for the rule
\newcommand{\plainplain}{%
\fancypagestyle{plain}{%
\renewcommand{\headrulewidth}{0pt}
\fancyhead[LO]{}
\fancyhead[RE]{}
}}
\newcommand{\myplain}{%
\fancypagestyle{plain}{%
\fancyhead[LO]{\bfseries\rightmark}
\fancyhead[RE]{\bfseries\leftmark}
\renewcommand{\headrulewidth}{0.5pt}
}}
\plainplain
\pagestyle{plain}
\begin{document}
\frontmatter
\pagenumbering{Roman}
\tableofcontents
\clearpage
\listoffigures
\clearpage
\chapter*{Abkürzungsverzeichnis}
\lipsum[1-4]
\clearpage
\listoftables
\clearpage
\mainmatter % implies arabic pagenumbering
\myplain
\pagestyle{plain}
\chapter{Introduction}
\lipsum[1-7]
\section{New Section}
\lipsum[8-14]
\clearpage
\plainplain
\pagestyle{plain}
\backmatter
\pagenumbering{roman}
\setcounter{page}{5}
\nocite{mybook1}
\bibliographystyle{plainnat}
\begin{filecontents}{bibliography.bib}
@book{mybook1,
title = {Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod
tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam,
quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo
consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse
cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non
proident, sunt in culpa qui officia deserunt mollit anim id est laborum. Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod
tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam,
quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo
consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse
cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non
proident, sunt in culpa qui officia deserunt mollit anim id est laborum.},
author = {myauthor},
year = {2010}
}
\end{filecontents}
\bibliography{bibliography}
\end{document}
If you instead comment out the first \pagestyle{fancy}, some of the section headlines become uppercase. Here is the same code again, but \pagestyle{fancy} is removed.
\documentclass[12pt, a4paper, oneside, onecolumn]{book}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[ngerman]{babel}
\usepackage[round]{natbib}
\usepackage{lipsum, filecontents}
\usepackage{fancyhdr}
% \pagestyle{fancy}
\renewcommand{\chaptermark}[1]{%
\markboth{#1}{}}
\renewcommand{\sectionmark}[1]{%
\markright{\thesection\ #1}}
\fancyhf{} % delete current header and footer
\fancyhead[LE,RO]{\bfseries\thepage}
\fancyhead[LO]{\bfseries\rightmark}
\fancyhead[RE]{\bfseries\leftmark}
\renewcommand{\headrulewidth}{0.5pt}
\renewcommand{\footrulewidth}{0pt}
\addtolength{\headheight}{0.5pt} % space for the rule
\newcommand{\plainplain}{%
\fancypagestyle{plain}{%
\renewcommand{\headrulewidth}{0pt}
\fancyhead[LO]{}
\fancyhead[RE]{}
}}
\newcommand{\myplain}{%
\fancypagestyle{plain}{%
\fancyhead[LO]{\bfseries\rightmark}
\fancyhead[RE]{\bfseries\leftmark}
\renewcommand{\headrulewidth}{0.5pt}
}}
\plainplain
\pagestyle{plain}
\begin{document}
\frontmatter
\pagenumbering{Roman}
\tableofcontents
\clearpage
\listoffigures
\clearpage
\chapter*{Abkürzungsverzeichnis}
\lipsum[1-4]
\clearpage
\listoftables
\clearpage
\mainmatter % implies arabic pagenumbering
\myplain
\pagestyle{plain}
\chapter{Introduction}
\lipsum[1-7]
\section{New Section}
\lipsum[8-14]
\clearpage
\plainplain
\pagestyle{plain}
\backmatter
\pagenumbering{roman}
\setcounter{page}{5}
\nocite{mybook1}
\bibliographystyle{plainnat}
\begin{filecontents}{bibliography.bib}
@book{mybook1,
title = {Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod
tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam,
quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo
consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse
cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non
proident, sunt in culpa qui officia deserunt mollit anim id est laborum. Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod
tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam,
quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo
consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse
cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non
proident, sunt in culpa qui officia deserunt mollit anim id est laborum.},
author = {myauthor},
year = {2010}
}
\end{filecontents}
\bibliography{bibliography}
\end{document}
I thought that \pagestyle{fancy} would be unnecessary there because the pagestyle is later defined to be \pagestyle{plain} and plain itself is redefined. Why do I have to set the pagestyle to something that I do not use at all when configuring fancyhdr?
\pagestyle{fancy}doesn't only set the page style, but also prepares LaTeX to using newly defined styles. Why are you redefining the plain style? It's better to have different names for different styles. – egreg Feb 04 '14 at 18:12plainstyle by default and I do not know how to change that, I rewroteplain. Every other approach led to strangely formatted pages after the first bibliography page. – Xiphias Feb 04 '14 at 18:13plainstyle? It's simply untrue. – egreg Feb 04 '14 at 18:30\pagestylechanges the default page style for all pages from that point on which don't have a special configuration. (The first page of chapters use a non-default style unless you redefine the command. Usually,plain. So to change that, you'd redefine the plain style e.g.\fancypagestyle{plain}{...}." Although you are probably right, as in your solution my chapter-first-pages changed, he made a point somehow ...? – Xiphias Feb 04 '14 at 18:40plain: http://tex.stackexchange.com/questions/158563/why-does-the-setspace-package-change-my-fancyhdr-design/158570?noredirect=1#comment361887_158570 – Xiphias Feb 04 '14 at 19:00setspacepackage change myfancyhdrdesign?? – Werner Jul 17 '14 at 23:52