Karlgren–Li reconstruction of Middle Chinese
The Karlgren–Li reconstruction of Middle Chinese was a representation of the sounds of Middle Chinese devised by Bernhard Karlgren and revised by Li Fang-Kuei in 1971, remedying a number of minor defects. Sources for Middle Chinese. The "Qieyun" rime dictionary was created by Lu Fayan in 601 as a guide to proper pronunciation, particularly for the reading of classic texts. The dictionary divided characters between the four tones, which were subdivided into 193 rhyme groups and then into homophone groups. The pronunciation of each homophone group is given by a fanqie formula , a pair of common characters respectively indicating the initial and final sounds of the syllable. Lu Fayan's work was very influential, and led to a series of expanded and corrected versions following the same structure, the most important of which is the "Guangyun" (1007–08). The "Qieyun" was thought lost until the mid-20th century, and scholars worked from the "Guangyun". Fortunately it was later found that the "Guangyun" had preserved the phonological system of the "Qieyun" with no significant change. The Qing dynasty scholar Chen Li analysed the fanqie spellings of the "Guangyun", determining which initial and final spellers represented  the same sounds, and thus enumerating the initials and finals of the underlying system. However this method gave no indication of how these were pronounced. A series of rime tables from the Song dynasty incorporated a more sophisticated analysis, though the language had changed since the time of the "Qieyun". The initials were identified and categorized by place and manner of articulation. Finals were classified into 16 rhyme classes ( "shè"). Within each rhyme class, syllables were classified as either "open" ( "kāi") or "closed" ( "hé"), as belonging to one of the four tones, and as belonging to one of four divisions  ( "děng"), indicated by rows of the table. The Qing philologists found that some of the finals of the rime dictionaries were always placed in the first row, some always in the second and some always in the fourth, and they were thus named finals of divisions I, II and IV respectively. The remaining finals were spread across the second, third and fourth rows, and were later called division III finals. Karlgren's reconstruction. Karlgren believed that the "Qieyun" system (represented by the "Guangyun") reflected the standard speech of the Sui-Tang capital Chang'an (modern Xi'an), which spread across the empire  except for Fujian. He attempted to determine the sounds of this "Ancient Chinese" (now called Middle Chinese) by applying the comparative method to data that he had collected on modern dialects, as well as the pronunciations of Chinese loanwords in other languages. Since the discovery of an early copy of the "Qieyun" in 1947, most scholars believe the dictionary reflects a combination of reading pronunciation standards from the capitals of the late Northern and Southern dynasties period. Karlgren's transcription involved a large number of consonants and vowels, many of them very unevenly distributed; indeed he disdained phonemic analysis as  a "craze". In a few cases he was unable to distinguish the pronunciations of ancient finals, and thus gave them identical transcriptions. His notation, based on Johan August Lundell's Swedish Dialect Alphabet, went through several revisions from his (1915–1926) through to the "Compendium of Phonetics in Ancient and Archaic Chinese" (1954). The same notation was used in his "Grammata Serica Recensa" (1957), a dictionary of Middle and Old Chinese that remains a standard reference, even though Karlgren's reconstruction of Old Chinese has been superseded by those of Li Fang-Kuei and William Baxter, among others. In the early  1970s, Li Fang-Kuei used an amended version of Karlgren's transcription as a point of departure for his reconstruction of Old Chinese phonology. Li addressed some of the criticisms of Karlgren's system, revising some initials and distinguishing finals that Karlgren had combined. Although Karlgren's view of Middle Chinese as a single spoken variety is no longer widely held, his transcription, as revised by Li, is still widely used as a notation for the "Qieyun" categories. Initials. Li replaced Karlgren's reversed apostrophe as an indicator of aspiration with a letter "h" for convenience. While Karlgren had originally  reconstructed the voiced stop initials as aspirated, Li treated them as unaspirated. Li also recast Karlgren's alveolar dentals as retroflex, citing a similar distribution to the retroflex affricates. Most scholars now believe that the "dź-" and "ź-" initials were interchanged in the rime tables, by which time they had merged. Vowels. Karlgren used a selection of vowel symbols from the Swedish Dialect Alphabet, here shown with IPA equivalents where different: In addition, "ậ" denotes a shorter (or centralized) variant of "â", while "ă", "ĕ" and "ə̆" denote shorter variants of "a", "e" and "ə", respectively. Finals. Karlgren divided the  division III finals into two groups: Li made a number of changes to remedy limitations of Karlgren's system: These were intended as purely notational devices, rather than suggested pronunciations. Karlgren's spellings for open finals, which could occur in the level, rising or departing tones, are given below, with the names of their "Guangyun" rhyme groups, and grouped by the broad rhyme classes ( "shè") of the rime tables. Where unrounded ("kāi") and rounded ("hé") finals occurred in the same "Guangyun" rhyme group, Karlgren marked the latter with a "-w-" medial. Where they were split between two "Guangyun" rhyme groups , he marked the rounded final with a "-u-" medial. Finals ending in nasals "-m", "-n" and "-ng" could occur in the level, rising or departing tones, with parallel finals ending in "-p", "-t" and "-k" placed in the entering tone. Tones. The rising tone was marked with a trailing colon, the departing tone with a trailing hyphen. The level and entering tones were unmarked. Coblin's revision. W. South Coblin made further simplifications, without sacrificing any contrasts: