I've tried to find out classification of English nouns. Common nouns have a number of types, such as countable, uncountable and collective. Everything's clear here, but I am confused by Proper Nouns.
Some sources say that proper nouns (e.g the name John - There are five Johnes here) can be countable, can be uncountable and even has plural tantum form (e.g. Alpes), but on the other hand there are sources saying that countable/uncountable and collective rules are applicable only to common nouns.
Do the proper nouns have the same set of rules as common nouns (except indefinite article) or it is just an informal usage of it?