who? Magnum + bw Swiss Alps + Olympus XA

Couple of years ago , I found an magnum photographers b/w photos on winter train tour of swiss alps , camera was olympus xa .

Who was he ? Which film and developer and timing he used ?

Thank you,
Umut

Erich Hartmann.
https://shootfilmridesteel.com/jumping-on-the-xa-wagon-blame-erich-hartmann/