Cita APA (7th ed.)
Liu, Y. (2020). COVID-19: Prevention Guideline. Smashwords.
Cita Chicago (17th ed.)
Liu, Yiqing. COVID-19: Prevention Guideline. Monterey, EUA: Smashwords, 2020.
Cita MLA (9th ed.)
Liu, Yiqing. COVID-19: Prevention Guideline. Smashwords, 2020.
Atenció: Aquestes cites poden no estar 100% correctes.