In 1970, after my arrival in the U.S., while studying English at the English Language Institute of the University of Michigan, my good fortune was that I coauthored a dynamics paper for the ASME conference in Columbus, OH . There, I met Professor Milton Chace and Professor John Uicker. Professor Chace asked me what are my future plans. I told him that I wanted to study in a graduate program. He told me that the University of Michigan is a good place, and he promised me that he would help me to stay there. A month later, I got a phone call from Professor Don Calahan, from the Electrical Engineering Department, inviting me for an interview. Soon after that, I was accepted as a graduate student having two advisors. Professor Milton Chace from the Mechanical Engineering Department and Professor Don Calahan from the Electrical and Computer Science Department. In our further discussions, Professor Calahan let me know about IBM's simulation program named advanced statistical analysis program (ASTAP) and its simulation tools . One of the tools was sparse matrix methodology. Professor Calahan also told me that he envisioned a program for mechanical system simulations that does not use matrix inversion or matrix multiplications. That is because they require too many computer operations and therefore are expensive and inefficient. He then continued to tell me to avoid multiplying numbers with zero because they required the same computer time as the multiplication of two nonzero numbers, and we know the result before the operations take place. It became clear to me the importance of the numerical efficiency. Based on our discussion, I had chosen for numerical integration of the implicit backward difference formula (BDF) known also as the Gear algorithm. My choice was due to the numerical stability of the implicit backward numerical integration methods. It also solves numerically stiff problems. Although one can seldom find numerically stiff mechanical systems. However, they do exist. During my studies at the University of Michigan, I met Pardip Sheth who finished his Ph.D. under the supervision of Professor Uicker. Pardip and I discussed a lot of problems and research of common interest. I also attended a graduate class in linear dynamics that Sheth taught.