 On this analysis, the antecedent to the ellipsis does not need to be a complete constituent (an entire verb phrase), but can be merely a catena (the verbs "say" and "thinking" in the above examples), which need not contain the ellipsis.As noted above, VP ellipsis is generally impossible if it would operate both backwards and upwards.There are also certain other restrictions on the possibility of ellipsis, although a complete theoretical analysis may be lacking.