Journal Article
Liang, Z.-C.; Gizon, L.; Birch, A.; Duvall, T.; Rajaguru, S. P.: Solar meridional circulation from twenty-one years of SOHO/MDI and SDO/HMI observations: Helioseismic travel times and forward modeling in the ray approximation. Astronomy and Astrophysics
619, A99 (2018)