Before revision:  This memory is introduced to the model by the assumption that consecutive waiting times are the analog of CTRW themselves. This way, we obtain the 'Continuous' Time Random Walk in Continuous Time Random Walk. Surprisingly, this type of process , only with the long-term memory within waiting times, can successfully describe slowly decaying nonlinear autocorrelation function of the stock market return .
After revision:  This memory is introduced to the model by the assumption that many consecutive time intervals can be the same. Surprisingly, in this process we can observe a slowly decaying nonlinear autocorrelation function of the stock market return .