Lenker, J. N. (1914). A popular appeal in three languages for a three-language education: English, Scandinavian, German (modern instead of dead tongues) by the Vietor Direct Method. Minneapolis: Luther Press.

Lenker, John Nicholas. A Popular Appeal in Three Languages for a Three-language Education: English, Scandinavian, German (modern Instead of Dead Tongues) By the Vietor Direct Method. Minneapolis: Luther Press, 1914.

Lenker, John Nicholas. A Popular Appeal in Three Languages for a Three-language Education: English, Scandinavian, German (modern Instead of Dead Tongues) By the Vietor Direct Method. Minneapolis: Luther Press, 1914.