the letter "đ". It also has six tones: "á", "à", "ả", "ã" and "ạ", the five tones used for vowels along with flat tone "a". Literature The first evidence of writing in Vietnam appeared after the Han conquest of Nanyue (111 BC) with the introducing of Old Chinese and Classical Chinese in modern-day North and Central Vietnam. They, however, only had been materialized in form of fragments, short sentences engraved on bricks and coins. The first surviving literature in Vietnam is the Sanskrit Võ Cạnh inscription (4th century AD) near Nha Trang, which belongs to either Funan or Chamic culture. Following Võ Cạnh is the Old Cham Đông Yên Châu inscription near Trà Kiệu, dating from late 4th century, was erected by King Bhadravarman I of Champa, and was written in Old Southern Brahmic script. It remains today as the oldest attested epigraph of any Southeast Asian language, predating Mon, Khmer, Malay by centuries. Historically Vietnamese literature was initially written in chữ Hán and then chữ Nôm. Literature using Nôm script began roughly in the 10th century. Up until the 21st century, there had been two components existing at the same time: works written in Literary Chinese (with poems and prose demonstrating Vietnamese history and realities; thus, they are regarded as Vietnamese literature) and works written in Nôm script (mostly poems). Since the 1920s, literature has been mainly composed in the national language script (Vietnamese alphabet) with profound renovations in form and category such as novels, new-style poems, short stories and dramas, and with diversity in artistic tendency. Written literature attained speedy development after the August Revolution, when it was directed by the Vietnamese Communist Party's guideline and focused on the people's fighting and work life. Classical literature include Truyện Kiều (The Tale of Kieu) (Nguyễn Du), Cung Oán Ngâm Khúc (Complaint of a Palace Maid) (Nguyễn Gia Thiều), Chinh phụ ngâm (Lament of the soldier's wife) (Đặng Trần Côn), and Quốc âm Thi Tập (Poetry Collection) (Nguyễn Trãi), all of which are transliterated or annotated in chữ Quốc ngữ. Some famous female poets include Hồ Xuân Hương, Đoàn Thị Điểm, and Bà Huyện Thanh Quan. Modern Vietnamese literature has developed from romanticism to realism, from heroism in wartime to all aspects of life, and developed into ordinary life of the Vietnamese. Poetry Vietnam has had a diverse range of cultural poetry throughout its history. Historically, Vietnamese poetry consists of