Harvard citation style: Is it "...as mentioned in Author (year)..." or "...as mentioned in (Author, year)"?

I know that you can distinguish two ways of referencing scientific work in the Harvard (or author-year) citation style:

1. 
   

   You cite the idea or work in general:

   
   

   "Recently, a new approach for SOME STUFF was demonstrated for the first time (Author, year)."

   
   


2. 
   

   You cite the author:

   
   

   "Recently, Author (year) demonstrated SOME STUFF for the first time."

   
   

However, what is the correct way, if you want to state that something was mentioned in a certain work?

"...as explained in Author (year)..." or "...as explained in (Author, year)..."?

My personal opinion would be the second option, because the idea is not located "in" the author, but "in" the work he published. But in our group opinions differ strongly on this one. Can anyone provide a reliable and authoritative resource?