  Let $r(G_1, G_2)$ be the Ramsey number of the two graphs $G_1$ and $G_2$. For
$n_1\ge n_2\ge 1$ let $S(n_1,n_2)$ be the double star given by
$V(S(n_1,n_2))=\{v_0,v_1,\ldots,v_{n_1},w_0,w_1,\ldots,w_{n_2}\}$ and
$E(S(n_1,n_2))=\{v_0v_1,\ldots,v_0v_{n_1},v_0w_0,w_0w_1,\ldots,w_0w_{n_2}\}$.
In this paper we determine $r(K_{1,m-1},$ $S(n_1,n_2))$ under certain
conditions. For $n\ge 6$ let $T_n^3=S(n-5,3)$, $T_n^{''}=(V,E_2)$ and
$T_n^{'''} =(V,E_3)$, where $V=\{v_0,v_1,\ldots,v_{n-1}\}$,
$E_2=\{v_0v_1,\ldots,v_0v_{n-4},v_1v_{n-3},v_1v_{n-2},$ $v_2v_{n-1}\}$ and
$E_3=\{v_0v_1,\ldots,v_0v_{n-4},v_1v_{n-3},v_2v_{n-2},v_3v_{n-1}\}$. We also
obtain explicit formulas for $r$ $(K_{1,m-1},T_n)$, $r(T_m',T_n)$ $(n\ge m+3)$,
$r(T_n,T_n)$, $r(T_n',T_n)$ and $r(P_n,T_n)$, where
$T_n\in\{T_n'',T_n''',T_n^3\}$, $P_n$ is the path on $n$ vertices and $T_n'$ is
the unique tree with $n$ vertices and maximal degree $n-2$.
