Verification of facts refers to the task of verifying textual content. Taking into account the growth of false information on the Internet, fact-checking becomes not only the activity of only journalists. The problem in computer-based fact-checking on the Internet is the lack of universal mathematical models for extracting useful textual information. Proposed the algorithms and mathematical models for extracting useful textual information in order to further verify facts. Presented results of experiments with the practical application of the developed mathematical model for extracting useful text from Internet resources.