--- a/style.sty	Sat Oct 01 23:34:37 2016 +0100
+++ b/style.sty	Sun Oct 02 14:07:42 2016 +0100
@@ -13,7 +13,10 @@
 \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