Complex sentence: However, three of them are duplicates after any variables common to a pair are "cancelled": the pairs labelled with asterisks instead of Roman numerals are duplicates of pairs (i)-(iii).
Split into simpler sentences: However, three of them are duplicates after any variables common to a pair are "cancelled". That is, the three undominated pairs that are not labelled with Roman numerals are duplicates of pairs (i)-(iii).