<timeline> ImageSize = width:700 height:auto barincrement:20 PlotArea = left:90 bottom:60 top:0 right:10 Alignbars = justify DateFormat = mm/dd/yyyy Period = from:09/20/1976 till:05/01/1996 TimeAxis = orientation:horizontal format:yyyy Legend = orientation:horizontal position:bottom ScaleMajor = increment:2 start:1977 ScaleMinor = increment:2 start:1978 .
LineData = at:11/13/1978 color:black layer:back at:09/07/1979 color:black layer:back at:08/01/1980 color:black layer:back at:06/06/1981 color:black layer:back at:11/05/1982 color:black layer:back at:06/08/1984 color:black layer:back at:04/21/1986 color:black layer:back at:03/02/1987 color:black layer:back at:09/05/1988 color:black layer:back at:06/10/1991 color:black layer:back at:01/17/1995 color:black layer:back .