Mule's foal fools genetics with “impossible” birth – The Denver Post
Why can't two donkeys reproduce? - Quora
Hybrid Infertility: Why Can't Mules Reproduce?
HYBRID EQUINES - MULES, MOLLIES AND HINNIES
SOLVED: Mules are the offspring of the mating of a horse and a donkey. Mules are unable to reproduce. A horse has a total of 64 chromosomes, whereas donkeys have 62 chromosomes.
Mule Facts
ACCOUNTS OF FERTILE MULES AND HINNIES
Mule's foal fools genetics with “impossible” birth – The Denver Post