How I can delete the line spacing?

Hello, 

For the reference formatting part, I want to delete the line that shown as arrow sign (I mean when you hit the enter, there is always the arrow sign).

I’ve tried to format the line spacing (configure bibliography-layout, single), but the one line spacing keep showing up. 

Everytime I add a reference, I have to manually delete the line spacing. 

How can I delete the line spacing? 

Thanks!