1. A computer-implemented method of facilitating queries of a topic-based-source-specific search system, the system being configured to collect information from predefined sources, wherein each of the predefined sources relates to a content topic and is associated with information items, the method being implemented by the system that includes one or more processors executing one or more computer program modules which, when executed, perform the method, the method comprising: receiving, by a query input module, a first portion of a query; determining, by a suggestion module, a first set of the predefined sources based on the first portion of the query; receiving, by the query input module, a second portion of the query; determining, by a suggestion module, a second set of the predefined sources based on the second portion of the query; and providing, by a user interface module, a group of suggestions relating to the second set of the predefined sources for presentation on a user interface.