\part{Rings}
\subimport{chapters/chapter-12/}{chapter-12.tex}
\subimport{chapters/chapter-13/}{chapter-13.tex}
\subimport{chapters/chapter-14/}{chapter-14.tex}
\subimport{chapters/chapter-15/}{chapter-15.tex}
\subimport{chapters/chapter-16/}{chapter-16.tex}
\subimport{chapters/chapter-17/}{chapter-17.tex}
\subimport{chapters/chapter-18/}{chapter-18.tex}