Graphology handwriting analysis has spawned several systems. Integrative graphology focuses on strokes and their relation to personality. Graphoanalysis was the most influential system in the United States, between 1929 and 2000. The Sistema de Xandró is another method of integrative graphology. Holistic graphology is based on form, movement, and use of space. The psychogram is another method which uses specific diagrams to analyze handwriting. The Personal Worth Chart is one such method developed by the Handwriting Consultants of San Diego during the early 1980s. The psychograph is an additional psychogram method. was developed by Leslie King during the 1970s. The Wittlich
What Is and What Should Never Be descending riff [of "What Is and What Should Never Be"] is amazing: It's like a bow is being drawn back, and then it releases. The rhythm of the vocals is almost like a rap. It's insane — one of their most psychedelic songs." This was also one of the first songs recorded by the band for which Robert Plant received writing credit. According to rock journalist Stephen Davis, the author of the Led Zeppelin biography "Hammer of the Gods: The Led Zeppelin Saga", the lyrics for this song reflect a romance Plant had with his wife's younger sister. "What Is