Examples of sequential models are the waterfall model and the V model. For these models there is a logical order in which the topics will become relevant during the time of an IT lifecycle.
The integration of QA & testing topics with sequential models is shown in below figure where the QA & testing topics are plotted on the sequential lifecycle activities.
The logical order of topics is from left to right (this can be seen as a timeline). This depicts for example that the topic of reviewing would normally start before the start of test execution, these activities then continue in parallel.