/usr/lib/erlang/erts-7.3/doc is in erlang-doc 1:18.3-dfsg-1ubuntu3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/erlang/erts-7.3/../../../share/doc/erlang-doc/erts-7.3/doc
/usr/lib/erlang/erts-7.3/../../../share/doc/erlang-doc/erts-7.3/doc