  The Kumjian-Pask algebra of a higher-rank graph generalises the Leavitt path
algebra of a directed graph. We extend the definition of Kumjian-Pask algebra
to row-finite higher-rank graphs $\Lambda$ with sources which satisfy a
local-convexity condition. After proving versions of the graded-uniqueness
theorem and the Cuntz-Krieger uniqueness theorem, we study the Kumjian-Pask
algebra of rank-2 Bratteli diagrams by studying certain finite subgraphs which
are locally convex. We show that the desourcification procedure of Farthing and
Webster yields a row-finite higher-rank graph $\tilde{\Lambda}$ without sources
such that the Kumjian-Pask algebras of $\tilde{\Lambda}$ and $\Lambda$ are
Morita equivalent. We then use the Morita equivalence to study the ideal
structure of the Kumjian-Pask algebra of $\Lambda$ by pulling the appropriate
results across the equivalence.
