Jews not only in Yiddish, but also other languages including Hebrew, English, French, Italian, Polish and Russian. They were written by concentration/death camp survivors, and also those who had been in hiding, or who had managed to flee from Nazi-held territories before or during the war, and sometimes they also described events after the Holocaust, including the liberation and rebuilding of lives in the aftermath of destruction. Survivor memoirs, like other personal accounts such as oral testimony and diaries, are a significant source of information for most scholars of the history of the Holocaust, complementing more traditional sources of historical information, and presenting events from the unique points of view of individual experiences within the much greater totality, and these accounts are essential to an understanding of the Holocaust experience. While historians and survivors themselves are aware that the retelling of experiences is subjective to the source of information and sharpness of memory, they are recognized as collectively having "a firm core of shared memory" and the main substance of the accounts does not negate minor contradictions and inaccuracies in some of the details. Yizkor books Yizkor (Remembrance) books were compiled and published by groups of survivors or landsmanshaft societies of former residents to memorialize lost family members and destroyed communities and was one of the earliest ways in which the Holocaust was communally commemorated. The first of these books appeared in the 1940s and almost all were typically published privately rather than by publishing companies. Over 1,000 books of this type are estimated to have been published, albeit in very limited quantities. Most of these books are written in Yiddish or Hebrew, while some also include sections in English or other languages, depending on where they were published. The first Yizkor books were published in the United States, mainly in Yiddish, the mother tongue of the landsmanschaften and Holocaust survivors. Beginning in the 1950s, after the mass immigration of Holocaust survivors to the newly independent State of Israel, most of the Yizkor books were published there, primarily between the mid-1950s and the mid-1970s. From the later 1970s, there was a decline in the number of collective memorial books but an increase in the number of survivors' personal memoirs. Most of the Yizkor books were devoted to the Eastern European Jewish communities in Poland, Russia, Lithuania, Latvia, Romania and Hungary, with fewer dedicated to the communities of south-eastern Europe. Since