High quality observations of the low degree p-modes exist for almost two complete solar cycles using the solar spectrophotometer Mark-I, located and operating at the Observatorio del Teide (Tenerife, Spain). In this work, the observations available have been re-analyzed over a much wider time interval than before. We analyze the time variation of the yearly frequency shift and its frequency dependence. This information will be used in order to average annual power spectra by removing the effect of the solar cycle. Using this average power spectrum, a new estimate of the rotational splittings is attempted.