Solidaridad Obrera
...that during the Spanish Civil War Solidaridad Obrera, published by an anarchist labor union, was Spain's highest-circulation newspaper?
...that during the <a href="./Spanish_Civil_War" id="mwBGM" rel="mw:WikiLink" title="Spanish Civil War">Spanish Civil War</a> <i id="mwBGQ"><b id="mwBGU"><a href="./Solidaridad_Obrera_(periodical)" id="mwBGY" rel="mw:WikiLink" title="Solidaridad Obrera (periodical)">Solidaridad Obrera</a></b></i>, published by an anarchist labor union, was Spain's highest-circulation newspaper?