Keep pulling the thread on Chris Olah.
Many of the most significant papers in machine learning in recent years, such as those for TensorFlow and AlphaGo, have resulted from collaborations of over 20 people.
Author contribution statements are a standard practice in many academic fields and are required by journals such as Nature and PLoS.
Research infrastructure such as Theano, Pytorch, TensorFlow, R, or Genome Analysis Toolkit should be cited when it is significantly built upon.
Datasets such as ImageNet should be cited when used in research.