The letters from Browning's sister Mariana were originally listed as 7 separate envelopes numbered OB/1/234-240; the rest of the family (except his mother's letters) were listed in a single group with the reference number OB/1/241-260. These envelopes have been rearranged so that the entire family appears in alphabetical order. As there were more people than reference numbers available, the last 5 envelopes all take the reference number OB/1/260/A with a letter following (e.g. OB/1/260a/A) to avoid extensive renumbering.