Factors Associated With the Availability of Virtual Consultations in Primary Care Across 20 Countries: Cross-Sectional Study - Gabriele Kerr; Geva Greenfield; Edmond Li; Thomas Beaney; Benedict W J Hayhoe; Josip Car; Ana Clavería; Claire Collins; Gustavo Gusso; Robert D Hoffman; Geronimo Jimenez; Tuomas H Koskela; et al. (Journal of Medical Internet Research)