Complex sentence: Let ("X " 0,"X " 1) be a compatible couple of complex Banach spaces, and assume that is dense in"X " 0 and in"X" 1.
Split into simpler sentences: Let ("X " 0,"X " 1) be a compatible couple of Banach spaces. Let be a compatible couple, and assume that is dense in"X " 0 and in"X" 1.