  We investigate the problem of locating the source of diffusion in complex
networks without complete knowledge of nodes' states. Some currently known
methods assume the information travels via a single, shortest path, which by
assumption is the fastest way. We show that such a method leads to the
overestimation of propagation time for synthetic and real networks, where
multiple shortest paths as well as longer paths between vertices exist. We
propose a new method of source estimation based on maximum likelihood
principle, that takes into account existence multiple shortest paths. It shows
up to 1.6 times higher accuracy in synthetic and real networks.
