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

Automated email sequences are sent to users after they take specific actions, such as signing up for an email newsletter or completing a purchase. These perfectly timed and crafted emails may seem ...

Jason Fernando is a professional investor and writer who enjoys tackling and communicating complex business and financial problems. Natalya Yashina is a CPA, DASM with over 12 years of experience in ...