docs: @Reference(authors = "E. B. Fowlkes, C. L. Mallows", //
        title = "A method for comparing two hierarchical clusterings", //
        booktitle = "Journal of the American Statistical Association, Vol. 78 Issue 383", //
        url = "https://doi.org/10.2307/2288117", //
        bibkey = "doi:10.2307/2288117")
    public double fowlkesMallows() {
      return FastMath.sqrt(precision() * recall());
    }