In 1823 Abel wrote a paper titled "a general representation of the possibility to integrate all differential formulas" (Norwegian: en alminnelig Fremstilling af Muligheten at integrere alle mulige Differential-Formler).
En 1823 escribiu un artigo titulado "Unha representación xeral da posibilidade de integrar todas as fórmulas diferenciais" (En alminnelig Fremstilling af Muligheten at integrere alle mulige Differential-Formler).