His work and tests regarding magnetism were repeated later on by Hopkinson and Kapp, who then elucidated the whole theory mathematically by means of formulae and constants. 弗兰克·刘易斯·戴尔.爱迪生的生平和发明.
Knowing the definitions, rules, formulae, etc. 约翰·杜威.民主与教育.
Hence the failure of attempts to apply arithmetical or algebraic formulae to logic. 柏拉图.理想国.