Those are good examples, butterbrot. But just to clarify, when you wrote that "plural is always ihre", you meant that "plural is always ihre in the nomintaive and accusative cases", right? In the plural ihr would be ihren in the dative case, and ihrer in the (seldom used) genitive case.
butterbrot gave some good examples. Here is a link to a website that explains which endings are used. It has some very good charts, that I have found to be quite helpful. (Note: ihr is an ein word, as noted in the explanation above the "ein" word chart.)
I don't know if you're still studying German or not, SolonasK, but if you are, or for others who have the same question, I put together a chart after reading though a particularly long thread that, in parts, touched on this same topic and had thoroughly confused me by the end of it. Sometimes a picture is worth a thousand words:
Keep in mind that this is an example where "ihr" starts a sentence. When it is in the middle of a sentence, its meaning is less ambiguous because capitalization of the letter "I" (or lack thereof) will narrow down the options of what it could be -- "her" or "their" if it is not capitalized and "your" (singular or plural, formal) if it is. The word "ihr" may also be used as a pronoun to mean "you" (plural, informal) as in "you all" or "y'all."
It may also help you to know that the possessive pronoun (e.g., my, our, her, their, your) must agree in gender, number, and case with the noun it modifies. In the example for this prompt, the noun Zeitungen is plural nominative and therefore "ihr" takes an "-e" ending. In my example, the noun is feminine, singular, nominative. If you don't already have a good chart to help you determine which ending to use, I also made one of those a while back, so I'll paste it below for you:
Keep in mind that the same endings would apply to "ihr" with a capital "I," but it would mean "your" (singular or plural, formal).
Hope that helps you and others see things more clearly now on this topic.