The entry used to say (and still says)

According to ABF 17 the statement is originally due to to

T. Fukami, S. Ishihara,

Almost Hermitian structure on $S^6$, Tohoku Math J. 7 (1955), 151–156 (doi:10.2748/tmj/1178245052)

There is this alternative attribution, which I have added now:

According to

- Alfred Gray, Paul S. Green, p. 2 of
*Sphere transitive structures and the triality automorphism*, Pacific J. Math. Volume 34, Number 1 (1970), 83-96 (euclid:1102976640)

the statement is originally due to

- Deane Montgomery, Hans Samelson,
*Transformation Groups of Spheres*, Annals of Mathematics Second Series, Vol. 44, No. 3 (Jul., 1943), pp. 454-470 (jstor:1968975)

But looking through it, it’s maybe not so easy to decide.

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