Two mathematicians have proved that a straightforward question—how hard is it to untie a knot?—has a complicated answer.

The @ symbol can also appear in regular formulas outside of tables when Excel thinks you're trying to reference a single value from a range. If you see it pop up unexpectedly, it usually means Excel ...

Among people in prison, adding CXR or CRP to symptom screen was more effective than symptom screen alone. In addition to ...