SQL Server 2012 :: How To Combine Data From Different Tables Using A Query

I have a set of tables that look like what I have shown below. How I can achieve the desired output ?

CREATE TABLE #ABC([Year] INT, [Month] INT,Customer Varchar(10), SalesofProductA INT);
CREATE TABLE #DEF([Year] INT, [Month] INT,Customer Varchar(10), SalesofProductB INT);
CREATE TABLE #GHI([Year] INT, [Month] INT,Customer Varchar(10), SalesofProductC INT);

INSERT #ABC VALUES (2013,1,'PPP',1);
INSERT #ABC VALUES (2013,1,'QQQ',2);
INSERT #ABC VALUES (2013,2,'PPP',3);

[Code] ....

I have a query currently that looks like this . @Month and @Year are supplied as parameters

SELECT
-- select the sum for each year/month combination using a correlated subquery (each result from the main query causes another data retrieval operation to be run)
(SELECT SUM(SalesofProductA) FROM #ABC WHERE [Year]=T.[Year] AND [Month]=T.[Month]) AS [Sum_SalesofProductA]

[Code] ...

Right now I see an output like this : for a particular value of @Month and @Year

SalesofProductA, SalesofProductB, SalesofProductC What I would like to see is :

[Customer],SalesofProductA, SalesofProductB, SalesofProductC

How it can be done ?