In the Roman gradual, on Passion Sunday, the tract follows the first reading and the gradual the second reading, rather than the other way around which is the case on every other Sunday. Good Friday is the same way. Why is this?
For Palm Sunday, see page 15 in Paul Turner's Glory in the Cross: Holy Week in the Third Edition of the Roman Missal (Collegeville: Liturgical Press, 2011). There's an extensive preview on Google Books.
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