Below is Fact Sheet #35 from the US Department of Labor regarding standards for joint employment under the Fair Labors Standards Act.
It matters to some Americans to have this available, so here it is. I have also indexed with labels to make it easier to find. I don't usually assign labels, but, this time I did.
This Fact Sheet is from January 2016. Evidently, the Trump Labor Secretary can't get his mind around it to write a new one.