Math-Mode – Editing Theorem Environments in LaTeX

Question

I have two questions about editing theorem environments on Tex.
I did not see concrete answers among answered questions, so I ask here mines, hoping that there are not frequently asked.

First, I would like to know how to create the left line form the underlined title and followed by a little line at the bottom of a theorem like on this picture :
Then, which packages are needed to do that – and in which order (I encountered some trouble with adding some packages together, something like incompatibility, especially with "hyperref" and "ntheorem" packages)?

I am not an expert at all with Tex, so an answer like "cut and past it in your code" will be satisfying!

Thanks.

Answer 1

You can do this with thmbox package

\documentclass{article}
\usepackage{thmbox}
\newtheorem[L]{thm}{Theorem}[section]
\newtheorem{lem}[thm]{Lemma}
\newtheorem[S]{cor}[thm]{Corollary}

\begin{document}

\begin{lem}{First resualt}
Here a lemma
\end{lem}

\begin{thm}{Important}
Great theorem
\end{thm}

\begin{cor}{Final}
Here the corollary
\end{cor}

\end{document}

for ntheorem compatibilite may be

\usepackage[amsmath,hyperref,thmmarks]{ntheorem}

or if amsthm theorem style is used

\usepackage[amsthm,amsmath,hyperref,thmmarks]{ntheorem}