Question: After graduatng college,  André Dreiding spent two years as a research assisant for a healthcare company headquartered in what city?

Context paragraphs:
Wockhardt Hospitals: Wockhardt Hospitals are one of the tertiary care, super speciality healthcare networks in India offering healthcare services.  The chain of hospitals is owned by the parent company Wockhardt Ltd., India's 5th largest Pharmaceutical and Healthcare company with a presence in 20 countries across the globe.  Wockhardt hospitals, originally called First hospitals and Heart Institute, were one of the early movers among corporate health-care chains in India.  The company was established in 1989 and it started its first operations with a medical center in Kolkata, 1989 and a heart hospital in Bangalore two years later.  Today the company has its presence across India with 9 multi speciality hospital networks.

Scio-tech: Scio-tech is a British biotechnology and consumer healthcare company headquartered in Harley Street, London, United Kingdom.

Positron Corporation: Positron Corporation is an American nuclear medicine healthcare company specializing in cardiac Positron Emission Tomography (PET) imaging.  Positron operates in a variety of business areas combining cardiac PET imaging technology, radiopharmaceuticals and radioisotopes.  Positron is headquartered in Westmont, Illinois and holds three facilities: a radioisotope manufacturing facility in Lubbock, Texas, a clinical and technical cardiovascular PET training institute in Niagara Falls, New York and an automation manufacturing facility in Fishers, Indiana.

André Dreiding: André S. Dreiding (22 June 1919 in Zürich – 24 December 2013 in Herrliberg near Zurich) was a Swiss chemist.  He finished his high school studies in Zürich and then studied at Columbia University in New York where he was awarded BS and MS degrees.  After two years as research assistant at Hoffmann-La Roche, he continued postgraduate studies at University of Michigan in Ann Arbor under professor Werner Emmanuel Bachmann, and was awarded his Ph.D. in 1947.  He remained at the university until 1949 as Rackham and Lloyd Postdoctoral Fellow.  From 1949 to 1954, Dreiding was assistant professor at Wayne University, Detroit Institute of Cancer Research.  He also temporarily took over Bachmann's teaching and research duties at the University of Michigan after Bachmann's death in 1951, and held them until 1952.  In 1954, Dreiding turned to Switzerland and University of Zurich, where he became professor, and stayed until his retirement in 1987, after which he has been emeritus professor.

EKF Diagnostics: EKF Diagnostics (Entwicklung, Konstruktion und Fertigung) is a publicly listed Healthcare company founded 1990 in Barleben, Germany and is currently headquartered in Cardiff, Wales, UK.

George M. Rapier III: George M. Rapier III, M.D., serves as Chairman and CEO of "WellMed Medical Management, Inc.", a diversified healthcare company that is one of the fastest growing enterprises in the nation and Physicians Health Choice, a physician-owned Medicare Advantage Organization contracted with the Centers for Medicare and Medicaid Services (CMS).  WellMed Medical Management is headquartered in San Antonio, TX, it is South Texas’ largest physician‐owned practice management company, specializing in senior health care, and the largest primary care provider for seniors in this region.

Medochemie: Medochemie Ltd is a multinational generics pharmaceutical and consumer healthcare company headquartered in Limassol, Cyprus.  Medochemie develops, licenses, manufactures, markets, and distributes branded generic products as well as their own patented brands.

Hoffmann-La Roche: F. Hoffmann-La Roche AG is a Swiss multinational healthcare company that operates worldwide under two divisions: Pharmaceuticals and Diagnostics.  Its holding company, Roche Holding AG, has bearer shares listed on the SIX Swiss Exchange.  The company headquarters are located in Basel.

Hayden Smith: Hayden Smith (born 10 April 1985) is a professional rugby union player for Esher Rugby Club in England, and also plays for the United States national rugby union team.  Smith also spent two years playing professional American football as a tight end for the New York Jets of the National Football League and also spent two years playing for Saracens FC in England.

Innovaccer: Innovaccer Inc. is a Silicon Valley-based healthcare company, founded by Abhinav Shashank, Kanav Hasija, and Sandeep Gupta that provides physician practices, hospitals, health systems, and other healthcare providers with population health management and Pay-for-performance solutions.  Innovaccer also provides solutions for care management, referral management, and patient engagement.  The company was founded in 2012 and is headquartered in Berkeley, California with an operational site in Noida, India.

Supporting paragraphs: André Dreiding Hoffmann-La Roche
Answer: Basel