--- a/style.sty	Thu Nov 17 16:21:56 2016 +0000
+++ b/style.sty	Fri Nov 18 18:47:02 2016 +0000
@@ -9,6 +9,14 @@
 \definecolor{darkblue}{rgb}{0,0,0.6}
 \usepackage[colorlinks=true,urlcolor=darkblue,linkcolor=darkblue]{hyperref}
 
+\newcommand{\ZERO}{\mbox{\bf 0}}
+\newcommand{\ONE}{\mbox{\bf 1}}
+\newcommand{\Left}{\textit{Left}}
+\newcommand{\Der}{\textit{Der}}
+\newcommand{\der}{\textit{der}}
+\newcommand{\Ders}{\textit{Ders}}
+\newcommand{\ders}{\textit{ders}}
+
 %%% for trees
 %% http://anorien.csc.warwick.ac.uk/mirrors/CTAN/graphics/pgf/contrib/forest/forest.pdf