This is a test file with some referenced equations, line
<span>$$ this \qquad(1)$$</span>

Some equations might be inside of text,
<span>$$ for example \qquad(2)$$</span> this one.

Some equations might be on start of paragraphs:

<span>$$ start \qquad(3)$$</span> of paragraph.

Other might be on separate paragraphs of their own:

<span>$$ separate \qquad(4)$$</span>

Some of those can be labelled:

This is a test file with some referenced equations, line <span
id="eq:0">$$ this \qquad(5)$$</span>

Some equations might be inside of text, <span
id="eq:1">$$ for example \qquad(6)$$</span> this one.

Some equations might be on start of paragraphs:

<span id="eq:2">$$ start \qquad(7)$$</span> of paragraph.

Other might be on separate paragraphs of their own:

<span id="eq:3">$$ separate \qquad(8)$$</span>

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