 Complete the following phrase:  Founded in 1956 by three former Massachusetts Institute of Technology professors  Howard Simpson, Werner Gumpertz, and Frank Heger  SGH specializes in structural design, historic preservation and evaluation of building exteriors. The firm has a reputation for assessing structural or interior damage to buildings. Nationally, SGH is recognized as an expert on the science and causes of structural failure. For example, when mirror-glass panels began falling off Bostons John Hancock Tower and had to be temporarily replaced with plywood in 1973, SGH was hired to analyze what went wrong. More recently, SGH was hired by the National Institute of Standards and Technology NIST to investigate the 