Consolidating companies

Hi,

I wanted to know the best way to get a consolidated list of companies that appear in all 3 years. Here's what I'm talking about:

Sheet 1 (2010) A, B, C, D, E
Sheet 2 (2011) A, B, C, D
Sheet 3 (2012) A, B, C
Sheet 4: Which is the sheet I'm doing my analysis - should show only A, B, and C since they are the only companies that show up (have data) for all 3 years

In this very simple example, I want to have a sheet to consolidate this and show A, B, and C - which appear in all 3 years. Since D and E aren't in all 3 years I don't want them to show up in the data set I'm working with in sheet 4. As you might imagine, there are many more companies in each year, (thousands) which makes it tricky, at least for me right now.

I think I know how to do this but I want the best, foolproof way to do this.

Appreciate your help.