Question: The NCR Corporation (originally National Cash Register) was taken over by what company in 1991?

Context paragraphs:
Symbios Logic: Symbios Logic was a manufacturer of SCSI host adapter chipsets and disk array storage subsystems.  It was originally established as a division of NCR Corporation in 1972, before NCR's takeover by AT&T Corporation in 1991.

NCR 304: The NCR 304, introduced in 1957, was National Cash Register (NCR)'s first transistor-based computer.  The 304 was developed and manufactured in cooperation with General Electric.

NCR Corporation: The NCR Corporation (originally National Cash Register) is an American computer hardware, software and electronics company that makes self-service kiosks, point-of-sale terminals, automated teller machines, check processing systems, barcode scanners, and business consumables.  They also provide IT maintenance support services.  NCR had been based in Dayton, Ohio, starting in 1884, but in June 2009 the company sold most of the Dayton properties and moved its headquarters to the Atlanta metropolitan area.  Currently the headquarters are in unincorporated Gwinnett County, Georgia, near Duluth and Alpharetta.  Future headquarters are planned for the end of 2017 at Technology Square (adjacent to the Georgia Institute of Technology) located in Atlanta.

United States Naval Computing Machine Laboratory: The United States Naval Computing Machine Laboratory was a highly secret design and manufacturing site for code-breaking machinery located in Building 26 of the National Cash Register (NCR) company in Dayton, Ohio and operated by the United States Navy during World War II.  It is now on the List of IEEE Milestones, and one of its machines is on display at the National Cryptologic Museum.

NCR VRX: VRX is an acronym for Virtual Resource eXecutive, a proprietary operating system on the NCR Criterion series, and later the V-8000 series of mainframe computers manufactured by NCR Corporation during the 1970s and 1980s.  It replaced the B3 Operating System originally distributed with the Criterion series, and inherited many of the features of the B4 Operating System from the high-end of the NCR Century series of computers.  VRX was upgraded in the late 1980s and 1990s to become VRX/E for use on the NCR 9800 series of computers.

William S. Anderson: William Summers Anderson (born March 29, 1919) was president and chairman of the National Cash Register Corp (NCR) from 1972 to 1984.

Carbonless copy paper: Carbonless copy paper (CCP), non-carbon copy paper, or NCR paper (No Carbon Required, taken from the initials of its creator, National Cash Register) is a type of coated paper designed to transfer information written on the front onto sheets beneath.  It was developed by chemists Lowell Schleicher and Barry Green, as an alternative to carbon paper and is sometimes misidentified as such.

Chalmers Automobile: Chalmers Motor Company was an American automobile company located in Detroit, Michigan.  It was named after Hugh Chalmers of the National Cash Register Company.  Like Maxwell, the brand is now owned by Chrysler.

Oakwood, Montgomery County, Ohio: Oakwood is a city in Montgomery County, Ohio, United States.  The population was 9,202 at the 2010 census.  Oakwood is part of the Dayton Metropolitan Statistical Area.  It was incorporated in 1908.  John Henry Patterson, industrialist and founder of the National Cash Register Corporation, is considered the "Father of Oakwood."

National Cash Register Building: The National Cash Register Building, commonly referred to as the St. Johns Theater & Pub, was a building that was first erected in St. Louis, Missouri, for the Louisiana Purchase Exposition in 1904 and then moved to Portland, Oregon, the next year for the Lewis and Clark Centennial Exposition.  It was moved a third and final time to the suburb of St. Johns, Oregon, which is now a part of Portland.  It was given to the St. Johns Congregational Society by the NCR Corporation.  It now houses a McMenamins theater and pub.

Supporting paragraphs: Symbios Logic NCR Corporation
Answer: AT&T Corporation