Charles' friendStrunk and White are not alone. The authors of Grammar Smart note (p. 122) that we should add an apostrophe and an "s" for proper nouns that ends in "s", such as
Yeats's poemAnd aside from a few exceptions, the Chicago Manual of Style and the Associated Press agree ("Apostrophe-S vs. Apostrophe: Forming Possessives of Words Ending in S (or an S Sound)"). Still skeptical? Consider the following "real life" examples from a wide-range of authors and disciplines (updated from previous posts):
Johann Arnason has pointed out that Jaspers's "most condensed statement" of the axial age, describing it as the moment when "man becomes conscious of Being as a whole, of himself and his limitations," and "experiences absoluteness in the depths of selfhood and in the lucidity of transcendence," is remarkably similar to Jaspers's own version of existential philosophy.
-- Robert N. Bellah, Religion in Human Evolution, p. 272
In using it to build a science of the materially extended world, Descartes missed the significance of empirical measurement and inductive mathematical principles in physics; he went so far as to dismiss Galileo’s law of gravity because it was merely empirical. Descartes’s methodological pronouncements missed the actual procedures of the scientific revolution as badly as Bacon’s. Nevertheless, Descartes’s deductive system became for a generation or more the leading emblem of the “mechanical philosophy”; his Principles of Philosophy in 1644 was the most comprehensive statement across the range of science, incorporating everything from physics, chemistry, and physiology to celestial mechanics into a single materialist system.
-- Randall Collins, The Sociology of Philosophies, p. 568
During our period at the abbey his hands were always covered with the dust of books, the gold of still-fresh illumination, or with fellowship substances he touched in Severinus’s infirmary.
-- Umberto Eco, The Name of the Rose, p. 17,
Anyone who chooses to believe something contrary to evidence that an overwhelming majority of people find overwhelmingly convincing... will not be convince... And so, with this book, I do not expect to convince anyone in that boat. What I do hope is to convince genuine seekers who really want to know how we know that Jesus did exist, as virtually every scholar of antiquity, of biblical studies, of classics, and of Christian origins in this country and, in fact, in the Western world agrees. Many of these scholars have no vested interest in the matter. As it turns out, I myself do not either. I am not a Christian, and I have no interest in promoting a Christian cause or a Christian agenda. I am an agnostic with atheist leanings, and my life and views of the world would be approximately the same whether or not Jesus existed. My beliefs would vary little. The answer to the question of Jesus's historical existence will not make me more or less happy, content, hopeful, likable, rich, famous, or immortal.
-- Bart Ehrman, Did Jesus Exist?, pp. 5-6
"Don't be silly, my boy. You can't have Peters's job."
-- Dick Francis, Flying Finish, p.19
He stowed a bottle of a local rotgut called Five Island Gin--nicknamed Five Ulcer Gin--in radioman Harry Brooks's gas mask holster.
-- Laura Hillenbrand, Unbroken, p. 90
I plunge into a maze of cobbled alleys and mews cottages that once comprised the Circus's outstation for Covert Operations -- or in the parlance, simply Marylebone.
-- John le Carre, A Legacy of Spies, p. 106
Over the course of a week Amos [Tversky] gave five different talks about his work with Danny, each aimed at a different group of academics. Each time the room was jammed--and fifteen years later, in 1987, when Biederman left Buffalo for the University of Minnesota, people were still talking about Amos's talks.
-- Michael Lewis, The Great Undoing, p. 205
Yet it is also at once clear not only that Rawls’s priorities are incompatible with Nozick’s in a way parallel to that in which B’s position is incompatible with A’s, but also that Rawls’s position is incommensurable with Nozick’s in a way similarly parallel to that in which B’s is incommensurable with A’s.
-- Alasdair MacIntyre, After Virtue: A Study in Moral Theory, p. 249
At the time, Aleander had seemed full of humanist promise. With Erasmus's encouragement, he had traveled to Paris and secured a position at the Sorbonne.
Michael Massing, Fatal Discord, p. 409
Note that religion is singular in James's definition and plural in Dennett's. James is describing an experience that he takes to be universal among religions of all descriptions, while Dennett sees religions as distinct 'social systems.'There are plenty of more examples, but surely these should suffice.
-- Marilynne Robinson, Absence of Mind, p. 8
But Harry was already pulling a roll of parchment from the owl's leg. He was so convinced that this letter had to be from Dumbledore, explaining everything -- the dementors, Mrs. Figg, what the Ministry was up to, how he, Dumbledore, intended to sort everything out -- that for the first time in his life he was disappointed to see Sirius's handwriting... "I can't stop the owls coming," Harry snapped, crushing Sirius's letter in his fist.
J. K. Rowling, Harry Potter and the Order of the Phoenix, p. 35