I'd like to create a task with multiple person responsible. How it's possible to write that in the request?

If I follow the documentation : 

Owner<input type="text" name="personresponsible" value="">(loginid/userid)

Basically, I write in my request that : personresponsible:3456768GHJ

However, If I want to add another persone, what the separator that I need to use?comma?

personresponsible:3456768GHJ,789078HFJS   Don't work

Thanks for you help