The time order of the morphemes or classes in the utterance can usually be indicated by their order from left to right in the diagram. Situations may arise, however, in which that order cannot be represented. Such is the case when the relative order is not simply sequential, e.g. in the staggering of 'R' and 'Pⁿ' or 'P˅': 'k-t-b' and '—a-' in 'ktab' ‘book’; here we can only indicate 'R' before or after 'Pⁿ' and P˅'. Such also is the case when there are special restrictions upon concurrence among morphemes which are not contiguous. Since special restrictions involve special horizontal bars in the chart, it is usually convenient to have the two classes involved placed right next to each other.
- Harris (1951), a pag.355