On the history of the Hopf problem

@article{Agricola2017OnTH,
  title={On the history of the Hopf problem},
  author={Ilka Agricola and Giovanni Bazzoni and Oliver Goertsches and Panagiotis Konstantis and Sonke Rollenske},
  journal={arXiv: History and Overview},
  year={2017}
}
This short note serves as a historical introduction to the Hopf problem: "Does there exist a complex structure on $S^6$?" This unsolved mathematical question was the subject of the Conference "MAM 1 $-$ (Non-)Existence of Complex Structures on $S^6$", which took place at Philipps-Universit\"at Marburg, Germany, between March 27th and March 30th, 2017. 
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