Bayesian Multilevel Quantile Regression // Fits Bayesian mixed- effects (multilevel) quantile regression models using the asymmetric Laplace working likelihood and Stan. Supports an 'lme4'-style formula interface with nested and crossed random effects, fitting one or several quantiles, post-hoc non- crossing rearrangement of fitted quantiles, and the Yang, Wang and He (2016) posterior-variance correction for valid frequentist inference from the (misspecified) asymmetric Laplace posterior.