A current example results from the political pressures within the predominantly Christian fundamentalist states of the USA where creationists favour the presentation of creation science (as it emerges from Biblical interpretation) taught alongside theories of biological evolution. This has led to the progressive dilution of references of evolution (treated as only a theory) in textbooks through a process of self-censorship by authors and publishers concerned to make their products acceptable to such important markets, with immediate consequences for the contents of those books also intended for distribution to other markets, in the USA and elsewhere. Thus in 1984, no mention was made of evolution in one sixth of the biology textbooks used in schools.