“…Over the years, a number of researchers have proposed improvements or alterations to the Guyan reduction, including Downs (1980), Flax (1975), Johnson et al (1980), Kidder (1973, Kim (1985), Kuhar and Stahle (1974), Leung (1978), Miller ( 1980), Paz ( 1983Paz ( , 1984, and Suarez and Singh (1992). In these works, discussed in more detail by Young (1994), the transformation connecting the master and secondary coordinates has not been improved on very much, and Guyan reduction is still the industry standard for doing direct model reduction.…”