The American Bell Association International, Inc. ( www.americanbell.org ) has information about Bells of Sarna on their website at http://www.americanbell.org/forum/viewtopic.php?f=19&t=656
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In salport city there is a woman looking at a picture in the Pokemon fanclub. Make sure the first Pokemon in your party has full happiness's. Then talk to her and she will give you the soothe bell.