Definition: This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.
Input: Significant legislative changes in the status of the szlachta, as defined by Robert Bideleux and Ian Jeffries, consist of its 1374 exemption from the land tax, a 1425 guarantee against the 'arbitrary arrests and/or seizure of property' of its members, a 1454 requirement that military forces and new taxes be approved by provincial Sejms, and statutes issued between 1496 and 1611 that prescribed the rights of commoners.
Output:
Who defined the significant legislative changes?