In this supplement to Chapter 2, we adtitionally discuss aspects of sampling in web surveys. For example, when drawing a simple random sample, it is convenient to use systematic sample selection, where we beforehand apply some sorting (e.g. according region, gender, type of unit), which can strongly improve the structure and representation of the sample. When the survey population is composed from distinct parts (e.g. countries, study programs, companies of different size, etc.), we should consider sampling independently according to sampling stratification theory.