1. https://www.bruker.com/products/mr/epr/e-scan.html
2. http://www.magnettech.de/esr-epr-spectrometer/ms-5000-esr-spectrometer.html
3. http://lab.adani.by/solutions/kategoriya-resheniy/epr-spektroskopiya/
4. http://www.keycom.co.jp/eproducts/esr/top2.html
5. http://www.epr-spectrometer.ru/eng/