Zumariyah, Z. Improving Mathematics Learning Outcomes in the Covid-19 Pandemic Era Through Contextual Teaching and Learning (CTL) Learning Models Using WhatsApp Groups for Class II Students of Kempong State Elementary School, Kapanewon Kalibawang, Kulon Progo Regency. Int. J. Chem. Educ. Res. 2022, 6, 117-122.