Are there an algorithm that for given weighted graph $G$, partition it into 2 cluster $C_1,C_2$ such that sum of diameters of two clusters minimized?

I find a paper with title

**“C. Monma and S. Suri, Partitioning points and graphs to minimize the maximum or the sum of
diameters”**

in some related papers but i can’t access to above paper to find out their’s algorithm. The above paper solve my problem in $O(n^2)$.