Telting, Aerts, Mathias (1997):
Fit amplitude and phase diagrams of multi-periodic star β Cep, with multi-periodic model:

•   Main mode:
    L=M=0 (radial)

•   Second mode:
    L=2,M=1 or L=M=1

  Multiple modes do not add linearly: for multi-periodic stars the model needs to be multi-periodic!