What Is and What Should Never Be and What Should Never Be" was performed live at Led Zeppelin concerts between 1969 and 1973. A live version taken from a performance at the Royal Albert Hall in 1970 can be seen on the "Led Zeppelin DVD". Another was included on disc two of the live triple album "How The West Was Won". Two more versions were included in BBC Sessions. What Is and What Should Never Be "What Is and What Should Never Be" is a song by English rock band Led Zeppelin. It was written by Jimmy Page and Robert Plant and was included as the second
Four Thirds system Thirds cameras came to an end after the introduction of the mirrorless Micro Four Thirds format. Discontinued models include: The Four Thirds lens mount is specified to be a bayonet type with a flange focal distance of 38.67 mm. There are currently around three dozen lenses for the Four Thirds System standard. Before announcing that it would stop production of Four Thirds lenses in early 2017, Olympus produced about 20 lenses for the Four Thirds System under their "Zuiko Digital" brand. They are divided into three grades — Standard, High Grade and Super High Grade. High Grade lenses have faster