How about cutting the last one and replacing with

There are many occasions, therefore, when several explorers are surprised,
and somewhat pained, on meeting each other at the Pole. Of such an
occasion the history of the “marginal revenue curve” presents a
striking example. This piece of apparatus plays a great part in my
work, and my book arose out of the attempt to apply it to various
problems, but I was not myself one of the many explorers who
arrived in rapid succession at this particular Pole.

Joan Robinson, _The Economics of Imperfect Competition_, p. vi.

Humberto Barreto