Title: Clemens
Content:  plant collector ; Mazie E. Clemens (1890s–1952), American journalist and WWI war correspondent ; Olivia Langdon Clemens (1845–1904), wife of Samuel Langhorne Clemens (Mark Twain) ; Orion Clemens (1825–1897), brother of Samuel Langhorne Clemens (Mark Twain) ; Paul Clemens (born 1988), American baseball player ; Roger Clemens (born 1962), American baseball player ; Mark Twain, pen name of Samuel Langhorne Clemens (1835–1910), American author ; Sherrard Clemens (1820–1881), American politician and lawyer ; Titus Flavius Clemens (consul), great-nephew of the Roman Emperor Vespasian and (as Flavius Clemens) a saint in the Greek Orthodox Church ; William Clemens (film director) (1905–1980), American film director 
Title: Olivia Langdon Clemens
Content:  Olivia Langdon Clemens (November 27, 1845 – June 5, 1904) was the wife of the American author Samuel Langhorne Clemens, better known as Mark Twain.
Title: Clara Clemens
Content:  Clara Langhorne Clemens Samossoud, formerly Clara Langhorne Clemens Gabrilowitsch (June 8, 1874 – November 19, 1962 ), was a daughter of Samuel Clemens, who wrote as Mark Twain. She was a contralto concert singer and she managed his estate and guarded his legacy after his death as his only surviving child. She was married first to Ossip Gabrilowitsch, then to Jacques Samossoud after Gabrilowitsch's death. She wrote biographies of Gabrilowitsch and of her father. In her later life, she became a Christian Scientist.
Title: Cindy Lovell
Content:  Lovell made news around the world when she discovered the long-sought boyhood signature of Samuel Langhorne Clemens on July 26, 2019 inside the Mark Twain Cave in Hannibal, Missouri where Clemens lived from the age of 4 to 17. She had looked for the signature for decades and discovered it during a special tour with fellow Twain scholars during the quadrennial Clemens Conference hosted by the Mark Twain Boyhood Home & Museum. Lovell and cave owner Linda Coleberd did not announce the discovery until experts had the opportunity to examine it. The signature was authenticated as belonging to Samuel Clemens by Twain scholars Alan Gribben and Kevin Mac Donnell after comparing signatures of Sam Clemens and his siblings from the time period the Clemens family lived in Hannibal. Lovell's first significant Twain discovery came during a visit to the Bermuda National Trust when she found an unsigned manuscript detailing the first time Clemens witnessed a cricket match tucked inside a scrapbook. The essay had been published in The Strand after Twain's death, but the whereabouts of the original manuscript were unknown. The manuscript was later exhibited at Masterworks Museum of Bermuda Art.
Title: James Clemens (lord mayor)
Content:  Clemens made three voyages to Angola in the 1750s, in addition to other slave runs, in 1767 he sent the Ranger under William Speers to acquire slaves in Angola and take them to Barbados. Also in 1767 he became a member of the town council of Liverpool, and was, from 1775-6, the Lord Mayor. While Lord Mayor he presented St Pauls, Stoneycroft with a two cwt (104 kg) bell.
Title: Clemens
Content:  (c. 1510 to 1515–1555 or 1556), Franco-Flemish composer of the Renaissance ; James Clemens (disambiguation), multiple people ; Jean Clemens (1880–1909), youngest daughter of Samuel Langhorne Clemens (Mark Twain) ; Jeremiah Clemens (1814–1865), U.S. senator and novelist ; Josef Clemens (born 1947), German bishop ; Joseph Clemens (1862–1936), American missionary and plant collector ; Joseph Clemens of Bavaria (1671–1723), German archbishop ; Kellen Clemens (born 1983), American football player ; Koby Clemens (born 1986), American baseball player ; Marcus Arrecinus Clemens (disambiguation), multiple people ; Martin Clemens, British World War II soldier and Solomon Islands coastwatcher ; Mary Strong Clemens (1873–1968), American botanist 
Title: James Clemens (lord mayor)
Content:  James Clemens (fl. 1750-1775) was a Liverpool, England merchant and shipowner, and Lord Mayor of Liverpool.
Title: Orion Clemens
Content:  Orion Clemens (July 17, 1825 – December 11, 1897) was the first and only Secretary of the Nevada Territory. His younger brother Samuel Langhorne Clemens became a famous author under the pen name Mark Twain.
Title: Jean Clemens
Content:  Jane Lampton "Jean" Clemens (July 26, 1880 &ndash; December 24, 1909) was the daughter of Samuel Langhorne Clemens (better known by his pen name Mark Twain) and Olivia Langdon Clemens. She drowned in a bathtub at Samuel's home on Christmas Eve 1909, likely due to a seizure.
Title: William Clemens (film director)
Content:  William Clemens (September 10, 1905 – April 29, 1980) was an American film director. Born in Saginaw, Michigan, Clemens began his Hollywood career as a film editor in 1931. His first directing project was Man Hunt in 1936. His major credits include On Dress Parade with the Dead End Kids, two Perry Mason mysteries (The Case of the Velvet Claws and The Case of the Stuttering Bishop), three films featuring detective Tom Lawrence, a.k.a. "The Falcon," four films based on the Nancy Drew series, and Calling Philo Vance in 1940. Clemens' final project was The Thirteenth Hour in 1947. He died in Los Angeles, California in 1980.

Question: what is samuel langhorne clemens well known for?
Answer: Lecturer.