1. Черговий випуск NAQCC NEWS (North American QRP CW Club) - http://www.naqcc.info/newsletter_current.pdf
2. N4EKV - Telegraph Keys - http://www.n4ekv.com/keys.asp
3. QYT KT-9900 - https://radioaficion.com/cms/qyt-kt-9900/
4. IARU Monitoring System Region 1 - https://www.iaru-r1.org/wp-content/uploads/2021/09/IARUMS-Newsletter-2021-08.pdf
5. SCI-6 PC Sound Card Interface Kit - https://www.unifiedmicro.com/sci6.htm
