The paper
Ueber die Fläche vom kleinsten Inhalt bei gegebener Begrenzungwas prepared for publication by K. Hattendorff, at Riemann's request, and was first published in the 13th volume of Abhandlungen der Königlichen Gesellschaft der Wissenschaften zu Göttingen (1867). The text made available here is from Bernhard Riemann's Gesammelte Matheamtische Werke, edited by Heinrich Weber (2nd Edition, Teubner 1892, pp. 301-333), It is available here in the following formats:
Links:
D.R. Wilkins