Please answer a question about the following article about Nanjing:

The current economy of the city is basically newly developed based on the past. Service industries are dominating, accounting for about 60 percent of the GDP of the city, and financial industry, culture industry and tourism industry are top 3 of them. Industries of information technology, energy saving and environmental protection, new energy, smart power grid and intelligent equipment manufacturing have become pillar industries. Big private firms include Suning, Yurun, Sanpower, Fuzhong, Hiteker, 5stars, Jinpu, Tiandi, CTTQ Pharmaceutical and Simcere Pharmaceutical. Big state-owned firms include Panda Electronics, Yangzi Petrochemical, Jinling Petrochemical, Nanjing Chemical, Nanjing Steel, Jincheng Motors, Jinling Pharmaceutical, Chenguang and NARI. The city has also attracted foreign investment, multinational firms such as Siemens, Ericsson, Volkswagen, Iveco, A.O. Smith, and Sharp have established their lines, and a number of multinationals such as Ford, IBM, Lucent, Samsung and SAP established research center there. Many China-based leading firms such as Huawei, ZTE and Lenovo have key R & D institutes in the city. Nanjing is an industrial technology research and development hub, hosting many R & D centers and institutions, especially in areas of electronics technology, information technology, computer software, biotechnology and pharmaceutical technology and new material technology.

Companies such as Ford, IBM, Lucent, Samsung and SAP have built what in Nanjing?
research center