# Reference inside sub equation to itself

Below is an example snippet of a proof in paper I am trying to reproduce. It seems. to be in a subequation environment, but it self references inside intertext.

How can I either self reference this, or continue the numbering? When I try using the functions above it gives me an error.

• \label and \ref can self reference easily, since they are created in one pass and used in the next. – John Kormylo Aug 21 '19 at 13:17
• Are you really using \intertext? I see no reason to. – egreg Aug 21 '19 at 13:51

Just use them:

\documentclass[]{article}

\usepackage[]{amsmath}

\begin{document}
\setcounter{equation}{16}
\begin{subequations}
$H(\omega)$ satisfies the following two properties:
\begin{align}
Conversely let $H(\omega)$ be a Fourier series satisfying \eqref{eq:prop:1}
$$\lvert H(\omega) \rvert \neq 0 \quad\text{for}\quad \omega\in[0,\pi/2]\text{ .}$$