Riemann’s habilitation paper Über die Darstellbarkeit einer Funktion durch eine trigonometrische Reihe (W. 227–265) (On the representability of a function by means of a trigonometric series) was completed in 1853, but was published by Dedekind only in 1868. If we consider not just its topic but also its origin,
contents, and influence, then we must assign the paper to the foundations of real analysis.