diff --git a/main.tex b/main.tex
index b330c9d..e66aaaf 100644
--- a/main.tex
+++ b/main.tex
@@ -45,6 +45,16 @@
 \graphicspath{{graphics/}}
 \DeclareGraphicsExtensions{.pdf, .png}
 
+\newcommand{\kat}[1]{\noindent\textcolor{material_red}{\textbf{Katerina:} #1}}
+\newcommand{\mk}[1]{\noindent\textcolor{material_green}{\textbf{Manos:} #1}}
+\newcommand{\dk}[1]{\noindent\textcolor{material_blue}{\textbf{Dimitris:} #1}}
+
+\newtheorem{definition}{Definition}
+\newtheorem{example}{Example}[section]
+\newtheorem{proposition}{Proposition}
+\newtheorem{theorem}{Theorem}
+\newtheorem{corollary}{Corollary}[theorem]
+
 \begin{document}
 
 \input{titlepage}