Regression with Skew-Normally Distributed Error Term // Models with skewnormally distributed and thus asymmetric error terms, implementing the methods developed in Badunenko and Henderson (2023) "Production analysis with asymmetric noise" doi:10.1007/s11123-023-00680-5. The package provides tools to estimate regression models with skewnormal error terms, allowing both the variance and skewness parameters to be heteroskedastic. It also includes a stochastic frontier framework that accommodates both i.i.d. and heteroskedastic inefficiency terms.