In 2011 Congressman Brian Bilbray (R-CA) responded to a request of some of his constituents and asked the Congressional Research Service to provide members of Congress with information on qualifiying for President.
The Congressional Research Service published a report for Congress: “Qualifications for President and the ‘Natural Born’ Citizenship Eligibility Requirement” in November, 2011.
https://fas.org/sgp/crs/misc/R42097.pdf
They did a far better and more accurate one back in the 1960s regarding George Romney. By the standards of that CRS report, Obama wouldn't have qualified.