| RankByTSource, TKey(IEnumerableTSource, FuncTSource, TKey) | Ranks each item in the sequence in descending ordering by a specified key using a default comparer |
| RankByTSource, TKey(IEnumerableTSource, FuncTSource, TKey, IComparerTKey) | Ranks each item in a sequence using a specified key and a caller-supplied comparer |