Who do I ask for a reference after a layoff?

The company closed and I am not sure how to reach former colleagues. There are 18 people counting on me, so I am trying to be careful. I have one former client who liked my work. Who did you use?

Ask former colleagues and supervisors in a short message and give them a summary of the job you are applying for.

A client reference worked well for me. It shows you deliver outside the company too.