This is a test file with some referenced equations, line

  ---------------------------------------------------------------- ------
                             $$ this $$                            $$(1)$
                                                                        $
  ---------------------------------------------------------------- ------

Some equations might be inside of text,

  ---------------------------------------------------------------- ------
                         $$ for example $$                         $$(2)$
                                                                        $
  ---------------------------------------------------------------- ------

this one.

Some equations might be on start of paragraphs:

  ---------------------------------------------------------------- ------
                            $$ start $$                            $$(3)$
                                                                        $
  ---------------------------------------------------------------- ------

of paragraph.

Other might be on separate paragraphs of their own:

  ---------------------------------------------------------------- ------
                           $$ separate $$                          $$(4)$
                                                                        $
  ---------------------------------------------------------------- ------

Some of those can be labelled:

This is a test file with some referenced equations, line

  ---------------------------------------------------------------- ------
                             $$ this $$                            $$(5)$
                                                                        $
  ---------------------------------------------------------------- ------

Some equations might be inside of text,

  ---------------------------------------------------------------- ------
                         $$ for example $$                         $$(6)$
                                                                        $
  ---------------------------------------------------------------- ------

this one.

Some equations might be on start of paragraphs:

  ---------------------------------------------------------------- ------
                            $$ start $$                            $$(7)$
                                                                        $
  ---------------------------------------------------------------- ------

of paragraph.

Other might be on separate paragraphs of their own:

  ---------------------------------------------------------------- ------
                           $$ separate $$                          $$(8)$
                                                                        $
  ---------------------------------------------------------------- ------

Then they can be referenced:

Individually eq. 5, eq. 6, eq. 7, eq. 8

Or in groups eqns. 5, 6, 8

Groups will be compacted eqns. 5-8