Citation for a knot theory statement

[BillKet]

Hello! Where can I find the source for this statement (i.e. a citation for it, ideally the original one): "any smooth k-sphere embedded in $R^n$ with 2n − 3k − 3 > 0 is unknotted". Thank you!

 

[fresh_42]

This paper here looks pretty close:
https://www.lms.ac.uk/sites/lms.ac.uk/files/1960 Unknotting spheres.pdf

 

[WWGD]

I thought knottedness ( of spheres) is a codimension-2 phenomenon.

 

[mathwonk]

Your impression is to some extent borne out by the second and third sentences of the paper by Zeeman, linked in post #2.