(1921). Ile węgla tracą Niemcy? =: Was Deutschland an Kohlen verliert? s.n..
Citazione stile Chigago Style (17a edizione)Ile Węgla Tracą Niemcy? =: Was Deutschland an Kohlen Verliert? [S.l.: s.n., 1921.
Citatione MLA (9a ed.)Ile Węgla Tracą Niemcy? =: Was Deutschland an Kohlen Verliert? s.n., 1921.
Attenzione: Queste citazioni potrebbero non essere precise al 100%.