How to Mindfulness Breathing?

Reference:

Ching, H. H., Koo, M., Tsai, T. H., & Chen, C. Y. (2015). Effects of a mindfulness meditation course on learning and cognitive performance among university students in Taiwan. Evidence-Based Complementary and Alternative Medicine, 2015.
Gallego, J., Aguilar-Parra, J. M., Cangas, A. J., Langer, Á. I., & Mañas, I. (2014). Effect of a mindfulness program on stress, anxiety and depression in university students. The Spanish journal of psychology, 17.