🌐EnglishEnglishDeutschEspañolFrançaisPortuguêsTürkçe日本語EntityQ1259814· pop 5· linked from 15 articlesNielsen–Schreier theoremtheorem that every subgroup of a free group is itself freeAvailable in 5 languagesFrançaisDeutschPortuguêsHebrewvia Wikidata sitelinks · CC0ConnectionszbMATH OpenEntityInternational Standard Book NumberEntityCategoriesAxiom of choiceProperties of groupsTheorems in algebraTheorems in group theory