comprehension question: Is Author: mama = Author: MaMa, Mang ?

If both abbreviations denote Massimo Mangialavori, why are two different abbreviations in use?

Example:

SKIN - Skin illnesses - eruptions - urticaria - allergic (3) Suggesta2 - goss.(1), helium(2) [Author: mama], petr.(2)

DREAMS - country - foreign (5) Suggesta2 - caps.(1), helium(2)[Author: MaMa,Mang], ind.(1), lach.(1), ozone(1)