When using the bibliographic search request, I cannot find publications with the keyword "x-ray" in the title. Why is that?

Currently, due to technical reasons, some queries with words that have special characters return no result. The workaround is to treat such a word like two words and use the proximity operator. Instead of (ti=x-ray) query, use (ti=x prox/distance=0/ordered=true ti=ray), which looks for titles with "x" immediately followed by "ray".