 <unk> @-@ <unk> was instrumental in developing the concept of " <unk> <unk> " , the idea that one should only purchase goods that are produced in an ethical way . His essay , " <unk> <unk> , " was selected for publication in Arthur <unk> 's Best Jewish Writing 2003 . A singer , cello and guitar player , he <unk> and performs Jewish music . 
