SQL Server Select Query to Find Duplicates within a file

Need a SQL Select query that will find duplicates within the same file on multiple columns.  Table is called Products.  
Two columns; Product_Code and Product_Source.    Need to find all records that have multiple occurances of Product_Code + Product_Source.

For example;

Product_Code       Product_Source
12345                    A
12345                    A                       ---> Duplicate
18888                    A
18888                    C                       ---> Not a duplicate record
44000                    D
99999                    C
99999                    C                     ---> Duplicate