Portal, EEP-Electrical Engineering; Edvard (31 Oct 2012). "Application of 4-pole Switchgear Devices". EEP - Electrical Engineering Portal (بالإنجليزية). Archived from the original on 2022-05-29. Retrieved 2022-12-06.
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Portal, EEP-Electrical Engineering; Edvard (31 Oct 2012). "Application of 4-pole Switchgear Devices". EEP - Electrical Engineering Portal (بالإنجليزية). Archived from the original on 2022-05-29. Retrieved 2022-12-06.