With AlphaSense, sources are filtered in two ways:
Filter Menu
Pick and choose which content you want to run your search against in the filter menu. You can hover over any quick filter and select "Only" to just search that specific content set, or select multiple from this quick menu.
To view the full sources menu, select "View All"
In Keyword Search with Source Operator
Add in:[content] + Tab
to easily filter for content right in the keyword search bar, removing the need to click 2 to 3 times into a filter menu.
Full Sources Menu:
To access the full Sources Menu, select "View All" in the vertical filter menu.