Sometimes you will want to read a text that is not complete. Hopefully the text that you are reading indicates this. If you are finding your text on Access to Insight through the regular sutta listings, it will say (excerpt) after the name. Be aware that many of the study guides on Access to Insight include excerpts without noting it. This is also true for many printed anthologies. If the text is from MN or DN and is only a page long, you can be sure it is an excerpt.
For dealing with missing repetitions, see the repetition page.