Extracting p-values for fixed effects from nlme/lme4 output in R

Extracting Fixed Effects Correlation from lmer Output: A Comparative Analysis of Approaches

Double Cross-Classified 3-Level Hierarchical Linear Models in R: A Comprehensive Guide

Understanding and Addressing the "Number of Levels" Error in Linear Mixed-Effects Models

Estimating Confidence Intervals for Fixed Effects in Generalized Linear Mixed Models Using bootMer: The Role of Random Effects and Alternative Methods.