 It is previously known that unweighted graphshave 2-, 4-, and 6-additive spanners containing (n^{3/2), }%DIFDELCMD < O%%% (n^{7/5), and O(n^{4/3}) edges, respectively.
<clarity>  It is previously known that unweighted graphshave 2-, 4-, and 6-additive spanners containing (n^{3/2), }%DIFDELCMD < O%%% (n^{7/5), and O(n^{4/3}) edges, respectively.
 It is previously known that unweighted graphshave 2-, 4-, and 6-additive spanners containing ), }%DIFDELCMD < O%%% (n^{7/5), and O(n^{4/3}) edges, respectively.