Footnotes
1.
[“The Alter Rebbe’s Siddur” is the popular name for the work whose formal title (as republished by Kehot, N.Y., 5725) is Tefillos MiKol HaShanah al pi Nussach HaAriZal im Pirush HaMilos al pi Dach. This title is commonly abbreviated to Siddur im Dach (“Siddur with [Commentaries of] Chassidus”).]
2.
See responsa of the Tzemach Tzedek, Orach Chayim 18:4; the responsa entitled Divrei Nechemiah, Orach Chayim 21; and for an extensive discussion of this entire subject see Shaar HaKollel 1:1, and the Introduction to Piskei HaSiddur, by R. Avraham Chayim Naeh.