Writing Lab, among others, uses the usual five levels, as described above, then repeats the Arabic numerals and lower-case letter surrounded by parentheses (round brackets) – I. A. 1. a. i. (1) (a) – and does not specify any lower levels, though "(i)" is usually next. In common practice, lower levels yet are usually Arabic numerals and lowercase letters again, and sometimes lower-case Roman again, with single parentheses – 1) a) i) – but usage varies. MLA style is sometimes incorrectly referred to as APA style, but the APA Publication Manual does not address outline formatting at all. A very different style recommended by The Chicago Manual of Style, based on the practice of the United States Congress in drafting legislation, suggests the following sequence, from the top to the seventh level (the only ones specified): I. A. 1. a) (1) (a) i) – capital Roman numerals with a period, capital letters with a period, Arabic numerals with a period, italic lowercase letters with a single parenthesis, Arabic numerals with a double parenthesis, italic lowercase letters with a double parenthesis, and italic lowercase Roman numerals with a single parentheses, though the italics are not required). Because of its use in the US Code and other US law books, many American lawyers consequently use this outline format. Another alternative scheme repeats all five levels with a single parenthesis for the second five – I) A) 1) a) i) – and then again with a double parenthesis for the third five – (I) (A) (1) (a) (i). Many oft-cited style guides besides the APA Publication Manual, including the AP Stylebook, the NYT Manual, Fowler, The Guardian Style Guide, and Strunk & White, are curiously silent on the topic. One side effect of the use of both Roman numerals and uppercase letters in all of these styles of outlining is that in most alphabets, "I." may be an item at both the top (A-head) and second (B-head) levels. This is usually not problematic because lower level items are usually referred to hierarchically. For example, the third sub-sub-item of the fourth sub-item of the second item is item II. D. 3. So, the ninth sub-item (letter-I) of the first item (Roman-I) is item I. I., and only the top level one is item I. Decimal outline The decimal outline format has the advantage of showing how every item at every level relates to the