References x other Sheets

References x other Sheets

Hello , 

I need to create a reference in 2 diferents files ... for example: 
The file A contain the targets.
The file B contains the sales.

I need to create a reference in file A with the sales to compare with the target.
or it´s necessary to create a way to import the informations to files.

Other question, if the File A and File B if they were the same file but in diferents sheets, Would it be possible to create this references ?

tks