The improvement of Self Immunity, Mental and Psychosocial Health to Prevent Covid-19 Infection in Elders in Surakarta IndonesiaArgyo Demartoto, Siti Zunariyah and Sri Hilmi PujihartatiE3S Web Conf., 202 (2020) 12007DOI: https://doi.org/10.1051/e3sconf/202020212007