Construction of a spanning tree with many leaves

It is well known [4] that any $n$ vertex graph of minimal degree 4 possess a spanning tree with at least $\frac25\cdot n$ vertices, which is asymptotically sharp bound. In current work we present a polynomial algorithm that finds in a graph with $k$ vertices of degree at least four and $k'$ vertices of degree 3 a spanning tree with the number of leaves at least $\lceil\frac25\cdot k+\frac2{15}\cdot k'\rceil$. Bibl. 13 titles.