Substitute digits for the letters

Puzzle Question:

Substitute digits for the letters to make the following addition problem true.
W H O S E
T E E T H
A R E
+ A S
-------------------
S W O R D S
Note that the leftmost letter can't be zero in any word. Also, there must be a one-to-one mapping between digits and letters. e.g. if you substitute 3 for the letter H, no other letter can be 3 and all other H in the puzzle must be 3.

Answer --

Solution of Puzzle:

It is obvious that S=1 and T=9.
Also, (H + E) should be greater than 10 and hence, (E + H + E) must 20. Thus, there are 3 possible values for (E, H) pair: (6, 8) or (7, 6) or (8, 4). Use trial-n-error and everything will fit-in.
W H O S E 2 8 5 1 6
T E E T H 9 6 6 9 8
A R E 4 7 6
+ A S + 4 1
------------------- -------------------
S W O R D S 1 2 5 7 3 1

Toughness:

Intermediate