On (Co-)morphisms of Lie Pseudoalgebras and Groupoids

We give a unified description of morphisms and comorphisms of Lie pseudoalgebras, showing that the both types of morphisms can be regarded as subalgebras of a Lie pseudoalgebra, called the $\psi$-sum. We also provide similar descriptions for morphisms and comorphisms of Lie algebroids and groupoids.