Pronouns such as ours, theirs, yours, hers, and its , do not take apostrophes to form a possessive. This is a very common mistake. Please punctuate accordingly. This is a very common mistake. We want you to get it right.
Punctuation also goes inside footnote numbers.
They are usually two sentences strung together without punctuation. It might be the object of a deceptively located prepositional phrase. The subject of the sentence is reference , not annotations . To correct it, pluralize the subject to agree with the plural verb, or use the singular verb is to agree with the singular subject, depending on your meaning. Sometimes it is not easy to decide when a subject is singular or plural.