Vyatkina, Nina; Johnson, Karen E. "German Modal Particles"(PDF). Center for Advanced Language Proficiency Education and Research – The Pennsylvania State University. Archived(PDF) from the original on 2019-07-01.
Lampp, Claire M. (2006). "Negation in modern Hindi-Urdu: the development of nahII". S2CID198686698. {{cite journal}}: Cite journal requires |journal= (help)
Vyatkina, Nina; Johnson, Karen E. "German Modal Particles"(PDF). Center for Advanced Language Proficiency Education and Research – The Pennsylvania State University. Archived(PDF) from the original on 2019-07-01.