Introduction to Multilevel Linear Models in Stata, part 1: xtmixed command
Introduction to multilevel linear models in Stata, part 2: Longitudinal data
Multilevel Panel Data Analysis Stata books
Statistics with Stata: Version 12, Eighth Edition, Chapter 15: Multilevel and Mixed-Effects Modeling
Lawrence C. Hamilton
0-8400-6463-2, 978-0-8400-6463-9, Cengage, 2013.
... Bridges the gap between statistical texts and the Stata documentation, Statistics with Stata demonstrates how to use Stata to perform a variety of tasks.