Before revision:  In a recent breakthrough, Le and Solomon (2019) established the precise dependencies on \varepsilon>0 and d\in N of the minimum lightness of an (1+\varepsilon) -spanner , and observed that additional Steiner points can substantially improve the lightness.
After revision:  In a recent breakthrough, Le and Solomon (2019) established the precise dependencies on \varepsilon>0 and d\in N of the minimum lightness of an (1+\varepsilon) -spanners , and observed that additional Steiner points can substantially improve the lightness.