Under pressure from their employers, documentalists may bias the collection of information and the ways through which it may be accessed. These practices may include: the refusal of access, the refusal to hold certain categories of document (if they are considered offensive to certain scientific, moral, religious or aesthetic principles), biased classification of documents (possibly to the point of rendering them unretrievable), tampering with documents (including forgery, theft and destruction of documents), idiosyncratric design of classification systems to render access incompatible with other documentation systems, dispensing inaccurate or misleading information on the contents of the collection and the availability of documents, reservation of documents for users in exchange for financial or other favours.