National Trust sponsored research on Whitehaven coalfield(ағыл.). — «Marchon quickly went over to an alternative process using anhydrite or gypsum (calcium sulphate), and producing cement as well as sulphuric acid; the anhydrite was mixed with shale or marl, and roasted in a kiln (a rotary metal-shelled piece of plant, rather than an earthfast structure) to produce sulphur trioxide gas plus cement clinker.» Басты дереккөзінен мұрағатталған 29 желтоқсан 2019. Тексерілді, 16 мамыр 2020.
National Trust sponsored research on Whitehaven coalfield(ағыл.). — «Marchon quickly went over to an alternative process using anhydrite or gypsum (calcium sulphate), and producing cement as well as sulphuric acid; the anhydrite was mixed with shale or marl, and roasted in a kiln (a rotary metal-shelled piece of plant, rather than an earthfast structure) to produce sulphur trioxide gas plus cement clinker.» Басты дереккөзінен мұрағатталған 29 желтоқсан 2019. Тексерілді, 16 мамыр 2020.
