REPEATED RECORDS

Why this SQL procedure gives contiguous repeated records ( 3 or 4 times ) ?
 
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ALTER PROCEDURE GetProductsOnPromotInDep
(@DepartmentID INT)
AS
SELECT   Product.ProductID, Title
FROM Product INNER JOIN  
(ProductCategory INNER JOIN
(Category INNER JOIN Department    ON Department.DepartmentID = Category.DepartmentID)
  ON ProductCategory.CategoryID = Category.CategoryID)
  ON Product.ProductID = ProductCategory.ProductID
WHERE Category.DepartmentID = @DepartmentID
AND ProductCategory.CategoryID = Category.CategoryID
AND Product.ProductID = ProductCategory.ProductID
AND Product.OnPromotion = 1
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