see_for_mobile_phones

https://en.wikipedia.org/wiki/National_conventions_for_writing_telephone_numbers
https://en.wikipedia.org/wiki/List_of_mobile_telephone_prefixes_by_country

-----------------------------------------------------------------------------------------------------------------------------------------------------------------
https://www.cm.com/blog/how-to-format-international-telephone-numbers/
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
https://en.wikipedia.org/wiki/E.164
https://libphonenumber.appspot.com/

https://stackoverflow.com/questions/15745545/is-there-a-standard-for-phone-numbers
https://en.wikipedia.org/wiki/List_of_mobile_telephone_prefixes_by_country