Question: What American dialiect known as Southern Mountain English has been extensively researched by linguist Walt Wolfram?

Context paragraphs:
Argentine snake-necked turtle: The Argentine snake-necked turtle, also known as the South American snake-necked turtle ("Hydromedusa tectifera") is a species of turtle, known for the long neck which gave it its name.  Despite appearances, the Argentine snake-necked turtle is probably more closely related to the Mata mata ("Chelus fimbriatus") than to the Australian snake-necked turtles in the genus "Chelodina".  It is found in northern Argentina, Uruguay, Paraguay, and southern Brazil.  Not much is known about them, as they have not been extensively researched.  They are a popular pet in the exotic pet trade.

Crabgrass Frontier: Crabgrass Frontier: The Suburbanization of the United States is a book written by historian Kenneth T. Jackson and published in 1985.  Extensively researched and referenced, the book takes into account factors that promoted suburbanization such as the availability of cheap land, construction methods, and transportation, as well as federal subsidies for highways and suburban housing.

Rotbav Archaeological Site: Rotbav “La Pârâuț” is a Bronze Age site in southeastern Transylvania, Romania, located at the southern border of the modern village of Rotbav, in Feldioara Commune, and 20 km north of Braşov, capital of the county by the same name.  The settlement of Rotbav is situated upon a high terrace formation above the Olt River.  Its importance lies in a long stratigraphy comprising the timespan from the Early Bronze Age to the Bronze Age / Iron Age transition.  It is the most extensively researched site of this period in the region.

The Rudolphs: Lloyd Rudolph and Susanne Rudolph, known together as the Rudolphs, are American academians who extensively researched on Indian history and democracy.

Bloeme Evers-Emden: Bloeme Evers-Emden (] ; 26 July 1926 – 18 July 2016) was a Dutch Jewish teacher and child psychologist who extensively researched the phenomenon of "hidden children" during World War II and wrote four books on the subject in the 1990s.  Her interest in the topic grew out of her own experiences during World War II, when she was forced to go into hiding from the Nazis and was subsequently arrested and deported to Auschwitz on the last transport leaving the Westerbork transit camp on 3 September 1944.  Together with her on the train were Anne Frank and her family, whom she had known in Amsterdam.  She was liberated on 8 May 1945.

Walt Wolfram: Walt Wolfram (born February 15, 1941) is a sociolinguist at North Carolina State University, specializing in social and ethnic dialects of American English.  He was one of the early pioneers in the study of urban African American English through his work in Detroit in 1969.  Since the 1960s he has authored or co-authored 20 books and more than 300 articles on variation in American English.  He was an active participant in the 1996 debate surrounding the Oakland Ebonics controversy, supporting the legitimacy of African American English as a systematic language system.  In addition to African American English, Wolfram has written extensively about Appalachian English, Puerto Rican English, Lumbee English, and on many dialects of North Carolina, particularly of rural, isolated communities such as Ocracoke Island.

Hurricane Debbie (1969): Hurricane Debbie was an intense and long-lived hurricane that formed during August 1969.  The fifth tropical cyclone, fourth named storm, third hurricane and second major hurricane of the 1969 Atlantic hurricane season, Debbie formed on August 14 in the southern Atlantic Ocean and took a general northwesterly path until turning northward into the central Atlantic.  The storm was characterized by numerous fluctuations in intensity, and it reached winds corresponding to Category 3 status on the Saffir–Simpson Hurricane Scale on four separate occasions.  The hurricane bypassed the island of Bermuda to the southeast on August 22, before ultimately brushing southeastern Newfoundland with strong winds.  It dissipated over the cold waters east of Greenland.  Although Debbie had little effect on land, it was extensively researched and was subject to a weather modification experiment by Project Stormfury, in which it was seeded with silver iodide.

Appalachian English: Appalachian English, also known in the United States as Southern Mountain English, is American English native to the Appalachian mountain region of the Eastern United States.  Historically, the term "Appalachian dialect" refers to a local English variety of southern Appalachia, though Appalachian English today geographically encompasses multiple varieties, predominantly including Western Pennsylvania English as spoken in northern Appalachia and regional Southern U.S. English as spoken in central and southern Appalachia.  In fact, the "Atlas of North American English" identifies the "Inland South" dialect region, in which Southern U.S. English's defining vowel shift is the most evolved, as centering squarely in southern Appalachia, around the cities of Knoxville and Chattanooga, Tennessee; Birmingham, Alabama; and Asheville, North Carolina.  All Appalachian English is rhotic and characterized by distinct phonology, morphology, syntax, and lexicon.  It is mostly oral but its features are also sometimes represented in literary works.

Mimic poison frog: Ranitomeya imitator (formerly "Dendrobates imitator"), is a species of poison dart frog found in the north-central region of eastern Peru.  Its common name is mimic poison frog, and it is one of the best known dart frogs.  It was discovered in the late 1980s by Rainer Schulte who later split it up into more subspecies; describing each as a specific color morph, and sometimes having a separate behavioral pattern.  The acoustics, morphs, and behavior of the species have been extensively researched.

San'yōdō: San'yōdō (山陽道 , literally, "southern mountain circuit" or "southern mountain region") is a Japanese geographical term.  It means both an ancient division of the country and the main road running through it.  The San'yōdō corresponds for the most part with the modern conception of the San'yō region.  This name derives from the idea that the southern side of the central mountain chain running through Honshū was the "sunny" side, while the northern side was the "shady" (山陰 "San'in") side.

Supporting paragraphs: Walt Wolfram Appalachian English
Answer: Appalachian English