Question:
Suppose the Haftorah is from Amos. Can one read from a klaf that is only Sefer Amos by itself? Or can one only read from a full set of Trei Asour in one scroll?
Answer:
Trei Asar is one sefer that has 12 parts to it, and if it is missing the other 11 Neviim it isn’t complete. The benefit of reading from a klaf is only if it is a whole sefer and not if it is only a part. Therefore, it would be better to read from a whole nach (or even a whole Trei Asar) that is printed then from such a klaf. This scenario presents itself, if one wants to read Sefer Yona from a klaf on Yom Kippur, that it is better to read from a whole nach or at least a whole Trei Asar.
Best Wishes.
Sources:
Baba Basra 14b, R’ Gershom ibid, Meiri (in shita Mekubetzes) ibid, Shulchan Aruch Y:D 283-1, Abarbenel in His introduction to Trei Asar (Hachakira Hateshi’is), Rama Mipano 20, Yerushalayim B’modaeha (Shabbos-2) pg. 189- 36. Also see Har Hamaor 1 pg. 51, who discusses this at length