Since its premiere in 2010, BBC’s Sherlock has continued to grow in popularity, appealing to fans on both sides of the Atlantic. The show’s creators, Steven Moffat (who also runs Doctor Who) and Mark Gatiss, were riding a train to Cardiff and discussing their mutual obsession with Sherlock Holmes when they imagined a version of the detective set in the modern day, the way he would have been to Sir Arthur Conan Doyle’s original readers. Their reverence for the source material is obvious; though the technology and setting of the series is 21st century, Moffat and Gatiss endeavor to write a show as close to canon as possible. Here are 15 references to the stories that you might have missed.

1. Criterion Coffee Cups

An old friend, Mike Stamford, recognizes John Watson when he’s walking in the park. In A Study in Scarlet, John runs into an old friend at the Criterion Bar after coming back from Afghanistan: “I was standing at the Criterion Bar, when someone tapped me on the shoulder and, turning round, I recognised young Stamford.”

In Sherlock, a similar encounter takes place in a park. But look very closely at the coffee cups John and Mike are holding: they say CRITERION.

2. The Cellphone Deductions

The deductions that Sherlock makes about John's cellphone when he meets him are taken almost directly from the encounter in The Sign of the Four in which Sherlock examines John’s pocket watch and deduces from the engraving, the scratches, and the scuffs around the keyhole that it was a gift from his brother.

“Look at the inner plate, which contains the keyhole. Look at the thousands of scratches all round the hole -- marks where the key has slipped. What sober man's key could have scored those grooves? But you will never see a drunkard's watch without them.”

In the BBC’s version, the scuffmarks are around the edges of the power connection where the charger plugs in. Of course, modern Sherlock does get one thing wrong: Harry Watson is John’s sister.

3. Sherlock’s Text Messages

The mysterious text messages Sherlock sends John in “A Study in Pink” are taken nearly word for word from a telegram the famous detective sends in Conan Doyle’s The Adventure of the Creeping Man:

“It was one Sunday evening early in September of the year 1903 that I received one of Holmes’s laconic messages: Come at once if convenient—if inconvenient come all the same. — S. H.”

4. Shooting the Wall

In "The Adventure of the Musgrave Ritual,” Conan Doyle wrote, "Holmes, in one of his queer humours, would sit in an armchair... and proceed to adorn the opposite wall with a patriotic V. R. done in bullet-pock" (V.R. standing for Victoria Regina.) Instead of Queen Elizabeth II’s initials, the television version of everyone’s favorite high-functioning sociopath shoots a smiley face into the wall instead.

5. The Clergyman Disguise

In the episode “A Scandal in Belgravia,” Sherlock tries to get into Irene Adler’s house by disguising himself as a priest who got mugged. Turns out, the costume is a favorite of the character. They took the disguise straight from “A Scandal in Bohemia,” the episode’s namesake story: "He returned in a few minutes in the character of an amiable and simple-minded Nonconformist clergyman.”

6. “None of the Cabs Would Take Me”

In the “Hounds of Baskerville” episode in the second series, Sherlock shows up at 221 Baker Street covered in blood, wielding a harpoon. “Well that was tedious,” he deadpans. It looks like he’s coming straight out of “The Adventure of Black Peter,” a short story in which Sherlock investigates the gruesome harpoon murder of an old sea captain.

7. The Titles of John’s Blog Posts

In the television series, the cases that John writes up on his blog are all analogous to original Conan Doyle short stories. “The Greek Interpreter” becomes “The Geek Interpreter.” “The Speckled Band”? “The Speckled Blonde.” And “The Naval Treaty” becomes “The Navel Treatment,” which, personally, sounds like a much more interesting murder.

8. Seven Percent Stronger

Although show creators Steven Moffat and Mark Gatiss spoke out about their efforts to depart from the emphasis on Sherlock Holmes’ drug habit, there is a subtle reference in “The Hounds of Baskerville” in Season 2. When Mrs. Hudson offers Sherlock tea, he retorts that he needs something stronger. “Seven percent stronger,” he adds under his breath, referring to the seven-percent solution of cocaine the detective favors in canon.

"Which is it today?" I asked, — "morphine or cocaine?"

He raised his eyes languidly from the old black-letter volume which he had opened. "It is cocaine," he said, — "a seven-per-cent solution. Would you care to try it?"

– ­­­The Sign of the Four

9. Dr. Verner

When John asks one of his new patients about his former doctor, the writers are making a subtle nod to the original short story “The Empty Hearse” in which Sherlock, after he returns from the dead, has his distant cousin, Dr. Verner, buy John’s old practice so he can come back to live with Sherlock at Baker Street again.

“A young doctor, named Verner, had purchased my small Kensington practice…an incident which only explained itself some years later, when I found that Verner was a distant relation of Holmes, and that it was my friend who had really found the money.”

–The Empty Hearse

10. The Porn Titles

A new patient of John’s claims to be the proprietor of a bookstand specializing in…lewd material, and he offers John some samples with titles like Tree Huggers, British Birds, and The Holy War (“sounds a bit dry, I know, but there’s this nun with all these holes in her habit…”). John assumes it’s Sherlock in yet another silly disguise and proceeds to attempt to rip the beard off (oops!) an actual man with a beard.

It’s a mistake anyone could’ve made, especially anyone who’s read Conan Doyle closely. In the literary version, Sherlock is disguised as an old bookseller, and he offers John books with nearly the exact same titles as the old man’s wares in the show.

“’Here's BRITISH BIRDS, and CATULLUS, and THE HOLY WAR—a bargain, every one of them…’

… I remember that as I picked them up, I observed the title of one of them, THE ORIGIN OF TREE WORSHIP, and it struck me that the fellow must be some poor bibliophile, who, either as a trade or as a hobby, was a collector of obscure volumes."

–The Adventure of the Empty House

11. “Dear me, Mr. Holmes. Dear me.”

The text message criminal mastermind Jim Moriarty sends to Sherlock in “A Scandal in Belgravia” takes its final phrase from an anonymous note Moriarty writes in the fourth and final Holmes novel by Conan Doyle, The Valley of Fear.

“Two months had gone by, and the case had to some extent passed from our minds. Then one morning there came an enigmatic note slipped into our letter box. "Dear me, Mr. Holmes. Dear me!" said this singular epistle. There was neither superscription nor signature. I laughed at the quaint message; but Holmes showed unwonted seriousness.”

12. Reading John’s Blog

When Mary reads aloud from John’s blog in “The Empty Hearse,” the passage she reads is almost identical to a sentence in The Sign of the Four:

“So swift, silent, and furtive were his movements, like those of a trained bloodhound picking out a scent, that I could not but think what a terrible criminal he would have made had he turned his energy and sagacity against the law instead of exerting them in its defence.”

13. “John or James Watson”

In “The Empty Hearse,” Mary receives jumbled anonymous text messages, which she recognizes as skip code. One of the phrases in the texts, “John or James Watson?” is a tongue-in-cheek reference to “The Man With the Twisted Lip,” the short story in which Mary calls her husband James instead of John.

That incident also prompted the fan-theory (embraced in the television show) that John’s middle name is Hamish, John’s Scottish counterpart. A code that uses every third word is also explained in “The Adventure of the Glory Scott.”

14. A.G.RA

Mary offers John a flash drive with all of the information about her actual identity, labeled (presumably with her initials) A.G.RA. Phonetically, the letters are an allusion to the Agra treasure, which plays a central role in The Sign of the Four, the Conan Doyle story that introduced the character of Mary Morstan.

15. Gavin? Graham? Geoff?

The character Gregory Lestrade is named for two characters in the original stories: Inspector Gregory and Inspector Lestrade. In canon, Lestrade’s first name is only revealed with the letter G., which accounts for the joke that Sherlock in the TV series can never remember the detective inspector’s actual name.