How can you listen to non-explicit songs on Itunes radio?

If you want to exclude explicit songs, and assuming that you are using a computer's iTunes, from iTunes 12 for Windows: Listen to iTunes Radio :

Customize a station

iTunes Radio might not play the specific song or artist you use to create a station, but you can provide examples of songs and artists you’d like to hear. You can also request that certain songs or artists never be played.

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Allow or disallow explicit content (on all stations): Click On or Off next to Allow Explicit (above My Stations).