Hartnell: ‘The Daleks were difficult to play to’
https://www.doctorwho.tv/news-and-features/hartnell-the-daleks-were-difficult-to-play-to
Malorie Blackman pens Seventh Doctor and Daleks story
https://www.doctorwho.tv/news-and-features/malorie-blackman-pens-seventh-doctor-and-daleks-story
Were the Daleks a potty idea?
https://www.theguardian.com/media/mediamonkeyblog/2013/feb/28/doctor-who-dalek
The Big Picture: Dalek invasion
https://www.bbc.co.uk/news/entertainment-arts-21492310
The Dalek Invasion of Earth 2011
https://www.doctorwhotv.co.uk/the-dalek-invasion-of-earth-2011-22829.htm