<https://www.alfreed-ph.com/2018/02/Atomic-physics-and-spectra-pdf.html>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<http://schema.org/WebPage>
<https://www.alfreed-ph.com/2018/02/Atomic-physics-and-spectra-pdf.html>