Sometimes multiple citations or "strings" are necessary.
Principle 1: When a series of citations includes material grouped after more than one signal, the signals should appear in the order in which they are listed in § 6-300.
Principle 2: Section 6-300 breaks signals (and their references) into four different "types": (a) supportive; (b) comparative; (c) contradictory; and (d) background. Signals of the same type must be strung together within a single citation sentence and separated by semicolons. According to The Bluebook signals of different types should be grouped in different citation sentences. In other words, a period should end the string of authorities indicating support, and any authorities in contradiction, preceded by the appropriate signal, should follow in a separate citation sentence. The ALWD Guide to Legal Citation allows all to be contained in a single sentence with only a semicolon separating the four different categories and their signals.
Principle 3: When more than one citation is preceded by the same signal, the citations are grouped by type in the following order:
* If the writing concerns the law of a particular state, citations to the constitution, statutes, cases, and regulations of that state should, however, precede the rest.
** Reflecting their academic focus both The Bluebook and the ALWD Guide to Legal Citation call for the circuits of the U.S. Courts of Appeals to be treated as a single court for this purpose and for the different districts of the U.S. District Courts to be lumped together as well. There are many practice situations where this approach is inappropriate. In a brief to the Second Circuit of the U.S. Courts of Appeals or a U.S. District Court on whom its decisions are binding, decisions of that circuit should be treated as one court, while those of other circuits can reasonably be merged together as those of a single court. Indeed, this approach, as applied to courts with subunits, is inappropriate in any context where decisions of all those circuits or districts or divisions do not carry the same precedential weight.