Do bring a USB cable as well as your charger cable for your laptop and phone.
Sometimes a USB cable will do, but then there are times when you’ll actually need to plug it into the socket to properly recharge your phone, tablet or computer. So Wibool of the LoC kindly supplied the following images to show you what can be used:
Two suggestions as a sidenote:
How about, instead of using pen and paper, you make use of the smartphone’s native dictaphone apps to take notes?
Have you considered bringing a powerbank? Phones’ batteries usually run low during the worst moments.