Deville, RobertGonzalo, R.Jaramillo Aguado, Jesús Ángel2023-06-202023-06-201999-010305-004110.1017/S0305004198003119https://hdl.handle.net/20.500.14352/57600We investigate the best order of smoothness of L-p(L-q). We prove in particular that there exists a C-infinity-smooth bump function on L-p(L-q) if and only if p and q are even integers and p is a multiple of q.journal articlehttp://journals.cambridge.org/abstract_S0305004198003119http://www.cambridge.org/metadata only access517.98Infinitely smooth bump functionAnálisis funcional y teoría de operadores