--headings beginning with the words Mine and Mining
3
-- See Also the narrower term Electric power systems Here are entered works on the complex assemblage of equipment and circuits for generating, transmitting, transforming, and distributing electric energy.
4
-- See Also the narrower term Electric utilities Here are entered economic works on the sale and distribution of electricity for lighting and power purposes.
-- See Also the narrower term Gas industry Here are entered works on industries based on natural or manufactured gas. Works on municipal or other agencies that distribute gas to consumers are entered under Gas companies. Works on the manufacture of gas are entered under Gas manufacture and works. --other headings beginning with the word Gas
