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This paper has been withdrawn. A significantly revised version will be posted in the near future.

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This paper has been withdrawn by the author, since proposed extensions are equivalent at any k to either wreath or direct product.

This paper has been withdrawn by the author, because it was merged into cs.HC/0508041

This paper has been withdrawn by the author due to text overlap with arXiv:1102.5004, as well as omission of proper citations to arXiv:1110.4655 and arXiv:1111.0313

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