\begingroup

\input{Envelope_3_ref/intro}
\input{Envelope_3_ref/lower_envelope_3}
\input{Envelope_3_ref/upper_envelope_3}
\input{Envelope_3_ref/lower_envelope_xy_monotone_3}
\input{Envelope_3_ref/upper_envelope_xy_monotone_3}
\input{Envelope_3_ref/EnvelopeTraits_3}
\input{Envelope_3_ref/Env_triangle_traits_3}
\input{Envelope_3_ref/Env_sphere_traits_3}
\input{Envelope_3_ref/Env_surface_data_traits_3}
\input{Envelope_3_ref/Env_plane_traits_3}
\input{Envelope_3_ref/Envelope_diagram_2}

\endgroup