The Rebbe's guidance on establishing the correct text of seforim — Tanya, the Siddur, Shulchan Aruch HaRav, Tanach and other works (IK = Igros Kodesh letter number):
The principle: sources, not assumptions. The text of a sefer must be established carefully from the best sources and not changed on assumption. Editors should compare several manuscripts, which often yields far greater accuracy (IK 1644). Tanya should be reprinted only as a photo-reproduction of the 5660 Tomchei Temimim edition reviewed by the Rebbe Rashab (IK 1495). Questions of spelling are settled by checking line by line against the early printings, especially those from the Alter Rebbe's lifetime (IK 3610).
Tanya and Chassidus. The spelling of "notzer" and "ratzon" (IK 222); "Eloka" in different sections of Tanya (IK 3610); the wording of prayers in Tanya and its halachic implications (IK 165); the sources of rabbinic sayings cited in chassidic works (IK 99); "Emek HaMelech" in Chassidus refers to R. Naftali Hertz's work printed in Amsterdam (IK 7858); textual variants in chassidic writings and a siddur (IK 6910).
Siddur, Shulchan Aruch HaRav and halachic works. Why Siddur Tehillas Hashem spells "sheva" with an aleph (IK 6071); variants in Shulchan Aruch HaRav on playing ball on Yom Tov (IK 430); citing the Alter Rebbe and the Tzemach Tzedek in halachic literature (IK 2005, 1424); on Shev Moshe and Dovev Siftei Yesheinim (IK 7096); on Etz HaChaim (IK 6870).
Tanach, the Sefer Torah and letter forms. "Petzua daka" and requests for facsimiles of manuscripts (IK 1668); the letter shapes according to the Alter Rebbe's tradition (IK 2382); reservations about printing the aleph-beis with tagin (IK 2160); the Jerusalem Tanach and variant names (IK 5853); the spelling of Pinchas with or without a yud (IK 8291); the reading of "Sheol" and "Avadon" (IK 9730); precise citation of sources in the Zohar and Tanna d'Vei Eliyahu (IK 2391); the great responsibility of editing a new accessible commentary on Tanach (IK 7488).
Authenticity and corrections. Letters attributed to the Rogatchover Gaon are not authentic, judging by style and content (IK 7171). Diagrams and measurements of the Beis HaMikdash in a published book must be corrected (IK 8527), as must errors in a historical article about the Alter Rebbe's economic activity (IK 380).
See also: Accuracy – Chassidus manuscripts: collecting and authenticating; Accuracy – History and biographies; Mitzvos in daily life – The Sefer Torah: writing, checking and dedicating; Jewish outreach – Publishing and spreading Torah books.