A '''Bk-tree''' is a [[metric trees|metric tree]] suggested by Burkhard and Keller {{ref|BK73}} specifically adapted to discrete [[metric space]]s.
For simplicity, let us consider '''integer''' discrete metric <math>\varrho(x,y)</math>. Then, Bk-tree is defined in the following way. An arbitrary element ''a'' is selected as root node. Root node may have zero or more subtrees. The ''k-th'' subtree is recursively built of all elements ''b'' such that 
<math>\varrho(a,b) = k</math>. Bk-trees can be used for approximate string matching in a dictionary {{ref|BN98}}.

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== References and external links ==
* {{note|BK73}} W. Burkhard and R. Keller. Some approaches to best-match file searching, CACM, 1973
* {{note|BN98}}  [http://www.dcc.uchile.cl/~gnavarro/ps/spire98.2.ps.gz Ricardo Baeza-Yates and Gonzalo Navarro. Fast Approximate String Matching in a Dictionary. Proc. SPIRE'98]

[[Category:Trees (structure)]]