  Let $G$ be a locally compact group with the group algebra $L^1(G)$ and $N$ be
a closed normal subgroup of $G$. Suppose that $\xi:N\to\mathbb{T}$ is a
continuous character and $L_\xi^1(G,N)$ is the $L^1$-space of all covariant
functions of $\xi$ on $G$. We showed that $L^1_\xi(G,N)$ is isometrically
isomorphic to a quotient space of $L^1(G)$. It is also proved that the dual
space $L^1_\xi(G,N)^*$ is isometrically isomorphic to $L^\infty_\xi(G,N)$.
