The Letter to <i>Optica</i>...which seems as substantial as many scientific papers: <a href="https://www.osapublishing.org/DirectPDFAccess/097C4470-E105-761F-9B08CC1D230C291E_351044/optica-3-10-1144.pdf?da=1&id=351044&seq=0&mobile=no" rel="nofollow">https://www.osapublishing.org/DirectPDFAccess/097C4470-E105-...</a>