Rules for Electrical questions and answers. Div. 4 Switchgear and substations A guide for study and preparation for testing knowledge. / Pravila ustroystva elektroustanovok v voprosakh i otvetakh. Razd. 4 Raspredelitelnye ustroystva i podstantsii posobie dlya izucheniya i podgotovki k proverke znaniy.