Cantilène (Jongen, Joseph)
It is unlikely that this work is public domain in the EU, or in any country where the copyright term is life-plus-70 years. However, it is in the public domain in Canada (where IMSLP is hosted) and other countries where the term is life-plus-50 years (like China, Japan, Korea and many others worldwide). As this work was first published before 1923 or failed to meet notice or renewal requirements to secure statutory copyright, it is very likely to be public domain in the USA as well.
Otto Gauß (1877-1970)
Orgel-Kompositionen aus alter und neuer Zeit
Regensburg: Alfred Coppenrath's Verlag (H. Pawelek), 1909/1910.
Orgelmusik des 19 Jahrhunderts, Heft 10:
Belgische und niederländische Komponisten
Altötting: Musikverlag Alfred Coppenrath, 1985.
*Gauß was the collection editor. It is unlikely he made any original contributions to pieces from composers who were living when the collection was issued.