https://digital.library.lse.ac.uk/Documents/Detail/report-on-the-census-of-production-for-1979.-pa361-electrical-machinery/442961
Report on the Census of Production for 1979. PA361 Electrical machinery - LSE Digital Library
https://digital.library.lse.ac.uk/Documents/Detail/report-on-the-census-of-production-for-1973.-pa361-electrical-machinery/432959
Report on the Census of Production for 1973. PA361 Electrical machinery - LSE Digital Library
https://digital.library.lse.ac.uk/Documents/Detail/report-on-the-census-of-production-for-1972.-pa361-electrical-machinery/431056
Report on the Census of Production for 1972. PA361 Electrical machinery - LSE Digital Library