The grid developed during decipherment by Michael Ventris and John Chadwick of phonetic values for syllabic signs is shown below. (Note that "q" represents labilized velar stops [ɡʷ, kʷ, kʷʰ], not a uvular stop as in IPA)  Initial consonants are in the leftmost column; vowels are in the top row beneath the title. The transcription of the syllable (it may not have been pronounced that way) is listed next to the sign along with Bennett's identifying number for the sign preceded by an asterisk (as was Ventris' and Chadwick's convention). In cases where the transcription of the sign remains in doubt, Bennett's number serves to identify the sign. The signs on the tablets and sealings often show considerable variation from each other and from the representations below. Discovery of the reasons for the variation and possible semantic differences is a topic of ongoing debate in Mycenaean studies. In addition to the grid, the first edition of "Documents in Mycenaean Greek" contained a number of other signs termed "homophones" because they appeared at that time to resemble the sounds of other syllables and were transcribed accordingly: "pa2" and "pa3" were presumed homophonous to "pa". Many of these were identified by the second edition and are shown in the "special values" below. The second edition relates: "It may be taken as axiomatic that there are no true homophones." The unconfirmed identifications of "*34" and "*35" as "ai2" and "ai3" were removed. "pa2" became "qa". Other values remain unknown, mainly because of scarcity of evidence concerning them. Note that *34 and *35 are mirror images of each other but whether this graphic relationship indicates a phonetic one remains unconfirmed. In recent times, CIPEM inherited the former authority of Bennett and the Wingspread Convention in deciding what signs are "confirmed" and how to officially represent the various sign categories. In editions of Mycenaean texts, the signs whose values have not been confirmed by CIPEM are always transcribed as numbers preceded by an asterisk (e.g., "*64"). CIPEM also allocates the numerical identifiers, and until such allocation, new signs (or obscured or mutilated signs) are transcribed as a bullet-point enclosed in square brackets: [•].