Steve's Bus & Train Page: £1.50 - That'll Do Nicely!
The Secret Tube Map That's Only Meant For TfL Employees | Londonist
Oyster card - Wikipedia
The Oyster 💳 Card Reader is Always Right! - YouTube
TfL on Twitter: "@JackThomasE4 Hi Jack Did you touch the pink reader at Hackney Central? This might explain the fare issue here. Regards, Darran https://t.co/YyIeoeaMyW" / Twitter
London Underground: The pink touch in points throughout the Tube which means TfL gives you cheaper fares - MyLondon
An Ode To The Oyster Card | Londonist
How to pay and where to buy tickets and Oyster - Transport for London
Oyster card - Wikipedia
Touch a pink card reader when changing trains - Transport for London