Query Help

[James Seymour]

I have been asked to write a query that lists all pairs of supplier numbers such that both suppliers are located in the same city. I have also been asked not to include any redundant or reversed pairs.

Here is a sample table:
+--------+---------+---------+----------+
| SUPPID | SNAME | SSTATUS | SCITY |
+--------+---------+---------+----------+
| S1 | Adams | 20 | Toronto |
| S2 | Barnes | 10 | Ottawa |
| S3 | Collins | 30 | Ottawa |
| S4 | Jones | 20 | Toronto |
| S5 | Emery | 30 | Kingston |
+--------+---------+---------+----------+

The Sample Return would be:
+--------+---------+
| SUPPID | SUPPID |
+--------+---------+
| S1 | S4 |
| S2 | S3 |
+--------+---------+

I have no idea how to tackle this query, any help would be appritiated.