Pull-up

Basics:

• https://www.youtube.com/watch?v=CdtrfXK7bcg

Tutorials:

• Calisthenicmovement, The Perfect Pull Up - Do it right!
• FitnessFAQs, Improve Pullups Instantly
• FitnessFAQs, How to do a Perfect Pullup

One-arm pull ups

• Calisthenicmovement, Master the One Arm Pull Up - One Arm Pull Up Tutorial, July 2016

Extreme pull ups

• https://www.youtube.com/watch?v=9FN4Z26kPVY

Scapular position:

• The Lean Berets, https://www.youtube.com/watch?v=CG5B_aXsucY

Misc:

• ATHLEAN-X™ , How to Do More Pullups INSTANTLY! (Pull Up Technique), October 30, 2013

Weighted

• Geek Climber, This Skinny Guy Trains 57 Days to Pull Up His Wife, March 2020