resources/metadata/373/altformats.csv - external/libphonenumber - Git at Google

 Format         ; Parent Format ; Comment
 XX XX XX XX    ; fmt1_2/3/3    ; "Alternate format for two-digit prefixes"
 [67]X XX XX XX ; fmt2_3/2/3    ; "Alternate mobile format"
 [67]X XXX XXX  ; fmt2_3/2/3    ; "Alternate format for three-digit prefixes"
	Format ; Parent Format ; Comment
	XX XX XX XX ; fmt1_2/3/3 ; "Alternate format for two-digit prefixes"
	[67]X XX XX XX ; fmt2_3/2/3 ; "Alternate mobile format"
	[67]X XXX XXX ; fmt2_3/2/3 ; "Alternate format for three-digit prefixes"