Defining a resource as Principal, secondary, or tertiary also can depend on how you are using the material. A newspaper post may be the two primary and secondary. The term cumulative case study stands for a set of earlier experiments, which may be collected from many methods like the internet, https://case-study-writing-help20580.angelinsblog.com/33980414/the-5-second-trick-for-hbr-case-study-help