Lang Wu is Professor of Statistics at the University of British Columbia in Vancouver, Canada. His research interest includes the analysis of longitudinal data (or panel data) and survival data when there are missing values, censored values, measurement errors, and outliers. Jin Diu is Professor of School of Data Sciences at Zhejiang University of Finance and Economics in Hangzhou, China. Her main focus is on multivariate data, longitudinal data (or panel data), functional data, and spatial data.