Representation of mathematical concepts in the ontology of scientific knowledge

Features of mathematical data domains in the context of creation of ontology of scientific data domains are considered. Examples from the developed thesaurus on the equations of the mixed type from the section of the equations with partial equations of mathematical physics are given. Special attention is paid to questions of representation and relevant support of the thesaurus of the addressee. It is offered to use specialized thesauruses where along with definitions in a natural language there are character expressions. This approach allows to specify a request, using mathematical entry in the TeX-notation irrespective of original language that leads to reduction of search noise and reduction of search time. The issue of why there is still insufficient amount of mathematical thesauruses created and their necessity for digital libraries along with other information resources is discussed. The example of creation of a thesaurus for separate mathematical data domain is given. The special difficulty consists in the description of the taxonomy (genus and species relations) in mathematical subject domains, one of the possible versions of the description of these communications for the equation of the mixed type is proposed.