+ +----++----+----+----+----+
+ | * || e0 | e1 | e2 | e3 |
+ +====++====+====+====+====+
+ | e0 || e0 | e1 | e2 | e3 |
+ +----++----+----+----+----+
+ | e1 || e1 | e0 | 0 | 0 |
+ +----++----+----+----+----+
+ | e2 || e2 | 0 | e0 | 0 |
+ +----++----+----+----+----+
+ | e3 || e3 | 0 | 0 | e0 |
+ +----++----+----+----+----+