Would somebody please help me with my sentences?
The authors found out that 68% of the ads adhere to the criteria of the X and Y guidelines and claimed the existing guidelines need to be strengthening to ensure the adherence of the advertisements to the guidelines. This evaluation is mainly base on an ill defined criteria and the advertisements that had been analysed in this study appeared before the Y guidelines being published which might affect the validity of the conclusion.
to be strengthening - strengthened
the adherence- no article
mainly base- based
an ill defined criteria- il-defined Also, if it is singualr, then it should be 'criterion', but if it's plural then the verb needs to changethat had been analysed in this study appeared- were/are analysed- you can use 'had appeared' if you like
being published- were