 Individual spots, more apparent on public radio, often are used to express personal appreciation for the station's programming, and often also offer family members or friend best wishes on a major life event such as a wedding, anniversary or birthday.Criticisms include inhibiting influences on public affairs programs (even self-censorship) where investigative journalism is featured and tendencies toward the use of non-artistic criteria in determining the selection of programs, such as symphony broadcasts on radio and theatrical productions on television.The Public Broadcasting Service (PBS) defines its "Program Underwriting Policy" in its PBS Redbook.