The definition of Lie group bundle is provided below:
Definition A Lie group bundle, or LGB, is a smooth fibre bundle (K,q,M) in which each fibre K_m=q^{-1}(m), and the fibre type G, has a Lie group structure, and for which there is an atlas {\psi_i: U_i \times G\to K_m} such that each \psi_{i,m}: G \to K_m, m\in U_i , is an isomorphism of Lie groups.
and
A morphism of LGBs from (K,q,M) to (K',q',M') is a morphism (F, f) of fibre bundles such that each F_m : K_m —> K'_{f(m)} is a morphism of Lie groups.