The onomastic evidence and glosses of Slavic words in foreign-language texts show no detectable regional differences during this period. During the Middle Common Slavic period, from perhaps 600 to 800, some dialectal differences existed, especially in peripheral dialects, but most sound changes still occurred uniformly. (For example, the Old Novgorod dialect did not exhibit the "second palatalization of velars" while all the other Slavic dialects did.) Reconstructed "Proto-Slavic" forms are normally from this period. It is thought that the distinction of long and short vowels by quality, normally reflected in "Proto-Slavic" reconstructed forms, occurred during this time: Greek transcriptions from the 5th and 6th centuries still indicate Common Slavic *o as "a". During the Late Common Slavic period, from 800 to 1000, conceptual sound changes (e.g. the conversion of "TORT" sequences into open syllables and the development of the neoacute accent) still occurred across the entire Slavic area, but often in dialectally differentiated ways. In addition, migrations of Uralic and Romance speaking peoples into modern Hungary and Romania created geographic separations between Slavic dialects. Written documents of the ninth, tenth and eleventh centuries demonstrate some local features. For example, the Freising monuments show a dialect which contains some phonetic and lexical elements peculiar to Slovenian dialects (e.g. rhotacism, the word "krilatec"). Significant continuous Slavic-language texts exist from this period, beginning with the extant Old Church Slavonic (OCS) texts, composed in the 9th century but copied in the 10th century. The end of the Common Slavic period is usually reckoned with the loss of weak yers, which occurred in Bulgaria 950 but did not reach Russia until 1150. This is clearly revealed in the texts themselves: During the century or so between the composition and copying of the OCS texts, the weak yers disappeared as vowels, and as a result, the texts show marked instability in their representation. (The main exception is the Codex Zographensis, copied just before yer loss.) On the other hand, the Old East Slavic texts represent the weak yers with almost complete etymological fidelity until nearly two centuries later. The terminology of these periods is not consistent. For example, Schenker speaks only of "Early Proto-Slavonic" (= Early Common Slavic, the period of entirely uniform developments) and "Late Proto-Slavonic" (= Middle and Late Common Slavic), with the latter period beginning with the second regressive palatalization, due to the differing outcomes of pre-Proto-Slavic *x.