olemus
vektorruum, mis ühtlasi on meetriline ruum
= a vector space that is also a metric space

ülevaateid
https://math.stackexchange.com/questions/2841855/relation-between-metric-spaces-normed-vector-spaces-and-inner-product-space

https://link.springer.com/chapter/10.1007%2F978-1-4757-2178-2_12

http://www.ams.org/journals/bull/1980-02-03/S0273-0979-1980-14790-4/S0273-0979-1980-14790-4.pdf

https://hackmd.io/@howayi/S1i6kUV1S/%2Fs%2FBkFyqFGJr