Sentence:  Thus in Mary wrote an account of the trip first strong stress on Mary marks Mary as the <WSD>first</WSD> in a series of people who wrote accounts of the trip , strong stress on wrote marks the writing as the first of a series of actions of Mary 's concerned with an account of her trip ( about which she may later have made speeches , for example ) , and strong stress on trip makes the trip the first of a series of subjects about which Mary wrote accounts . 
Meaning of the word marked with <WSD> tags:  the first element in a countable series