It seems odd seeing a death place being Cambridge, MA and seeing a Specific date: May 28, 1707
Sarah was born and lived in Connecticut and had her cchildren in Canterbury. What proves death in Cambridge, MA? Her living children all lived in Connecticut when she died.
Find A Grave cites a book under copyright for data in provides:
– 1707
– Canterbury, Windham County, Connecticut, USA
– https://www.findagrave.com/memorial/81254109/sarah-backus
However, the quoted matter posted there doesn't mention this death year and place.
Backus, Reno Warburton. "The Backus Families of Early New England", 1966, p.12 – https://search.worldcat.org/title/1342165814
Whether this book cites gives further information isn't knowable without access to the book.
If there's specifically sure evidence for Sarah's death date and place, it would probably be found at AmericanAncestors (for someone paying to have access to it) or in other books under copyright protection such as:
"The Connecticut Nutmegger:, Volume 29 (1996) — https://search.worldcat.org/title/4428851
"The Spencers of the Great Migration", Volume 1 (2008) — https://search.worldcat.org/title/1011746047
