First printing of the Zohar, the fundamental work of the Kabbalah (Jewish esoteric and mystical teachings), authored by the Talmudic sage, Rabbi Shimon Bar Yochai.
Links: The Kabbalah
Av 20 is the anniversary of the passing of the Lubavitcher Rebbe's father, Rabbi Levi Yitzchak Schneerson (1878-1944), in Alma Ata (currently Almaty), Kazakhstan. Rabbi Levi Yitzchak was Chief Rabbi of Yekaterinoslav (currently Dnipro), Ukraine, and was arrested and exiled to Kazakhstan by the Stalinist regime as a result of his work to preserve Jewish life in the Soviet Union.
Links:
A Brief Biography
Rebbetzin Chana Scneerson's biography, which includes her account of her husband's heroism, arrest and passing.
People might tell you, “When you come to work, leave your spirituality at home. Don’t bother us with your peculiar lifestyle, your ethics, search for meaning . . . That’s all nice, but this is business. This is the real world.”
There is only one real world, and it belongs to one real G‑d.