Double Sudoku (Fun With Sudoku #7)

This Sudoku first time I saw in World Sudoku Championship 2009 (Puzzle C4). This puzzle I created for the team India practice. At that time this puzzle was known by the name Duo Sudoku. 
Now this puzzle type is appearing in WPF Sudoku Grand Prix Finals along with Classic Sudoku, Trimino Sudoku, Irregular Sudoku, and Palindrome Sudoku. All of the other types of Sudoku I have already published in this blog. This Double Sudoku, I am republishing as 7th Sudoku under Fun With Sudoku Series, wishing all my friends who are part of this WPF final Best of Luck for finals.

Rules of Double Sudoku

Fill in the grid so that every row, every column, and every box 2x4 contains all digits 1 through 4 twice. Cells with the same digits may not touch each other neither horizontally nor vertically.

Double Sudoku (Fun With Sudoku #7)

Double Sudoku (Fun With Sudoku #7) Solution

Previous Fun With Sudoku Series Puzzle: Odd/Even Count Sudoku

Next Fun With Sudoku Series Puzzle: Odd Sudoku

Solution of Quad Max Difference Sudoku (Daily Sudoku League #50)

Quad Max Difference Sudoku (Daily Sudoku League #50) Solution