Excellent article abut BK-Trees

I love when ideas are presented in a simple way. BK-Trees are well known structures, but in a normal work as a typical programmer, when I need to implement a more advanced search that MS SQL or SOLR.NET (lucene) allows, I tend to do it in a simple way - by result combination of some sub queries. This approach makes me forget about some not often used data structures in a "day time" job. And when I find an article that is easy to follow, light in a form, and cool in a subjects that it touches, I simple love it.