\begingroup

\input{Envelope_2_ref/intro}
\input{Envelope_2_ref/lower_envelope_2}
\input{Envelope_2_ref/upper_envelope_2}
\input{Envelope_2_ref/lower_envelope_x_monotone_2}
\input{Envelope_2_ref/upper_envelope_x_monotone_2}
\input{Envelope_2_ref/EnvelopeDiagram}
\input{Envelope_2_ref/EnvDiagVertex}
\input{Envelope_2_ref/EnvDiagEdge}
\input{Envelope_2_ref/Envelope_diagram}
\endgroup