Please solve the programming task below using a self-contained code snippet in a markdown code block.

Given an array of string words, return all strings in words that is a substring of another word. You can return the answer in any order.
A substring is a contiguous sequence of characters within a string
 
Please complete the following python code precisely:
```python
class Solution:
    def stringMatching(self, words: List[str]) -> List[str]:
```