Great question. We now see that this wasn’t clear in the problem description as originally written! The 3-page limit for your Executive Summary includes references (and any figures or tables). We don’t require any particular format for references - you are free to save space through your choice of a reference style or by simply using hyperlinks. Note that there is not a page limit for notebooks.
The final submission will have a 3-page limit, too. The goal of the executive summary is to provide a succinct overview of the key findings and ideas from the analysis. Those ideas do not have to be fully explained, justified, or elaborated on in that summary, but should be in the notebook (where space is not limited).