The Siddur was expanded in 1917 under Chief Rabbi Joseph Hertz; 1934 saw a "continuous" version, minimising the need for cross-reference, and which also incorporated additional material. The 1962 Second Edition, under Chief Rabbi Israel Brodie, was completely re-typeset; also the translation was amended where it had become unclear or archaic, and further additional material had been introduced. The Centenary Edition of 1990 saw an extensively revised translation by Rabbi Eli Cashdan, and also included a series of explanatory notes by Chief Rabbi Lord Jakobovits. In 2006, Chief Rabbi Jonathan Sacks penned a new translation, with commentary, instructions, laws & rubrics; this Fourth Edition formed the basis for the Koren Sacks Siddur published 2009.