list does not exist at site ?

Hi,

I am using SharePoint Server 2013 Client Components SDK  .

C# can read main list ok. But how do I  access a sublist ?

In a browser , I see the sublist by clicking a down arrow  to the right of the list , and choosing from a list of lists)

Listxdoesnot exist at site with URL YY

I tried to concatenate GetByTitle(list/sublist) but that didn't work. 

Any ideas?