Price (1984), the Romance lects had split apart enough to be able to speak of separate Gallo-Romance, Ibero-Romance, Italo-Romance and Eastern Romance languages. Some researchers have postulated that the major divergences in the spoken dialects began or accelerated considerably in the 5th century, as the formerly widespread and efficient communication networks of the Western Roman Empire rapidly broke down, leading to the total disappearance of the Western Roman Empire by the end of the century. The critical period between the 5th–10th centuries AD is poorly documented because little or no writing from the chaotic "Dark Ages" of the 5th–8th centuries has survived, and writing after that time was in consciously classicized Medieval Latin, with vernacular writing only beginning in earnest in the 11th or 12th century. An exception such as the Oaths of Strasbourg is evidence that by the ninth century effective communication with a non-learnèd audience was carried out in evolved Romance. A language that was closely related to medieval Romanian was spoken during the Dark Ages by Vlachs in the Balkans, Herzegovina, Dalmatia (Morlachs), Ukraine (Hutsuls), Poland (Gorals), Slovakia, and Czech Moravia, but gradually these communities lost their maternal language. Recognition of the vernaculars Between the 10th and 13th centuries, some local vernaculars developed a written form and began to supplant Latin in many of its roles. In some countries, such as Portugal, this transition was expedited by force of law; whereas in others, such as Italy, many prominent poets and writers used the vernacular of their own accord – some of the most famous in Italy being Giacomo da Lentini and Dante Alighieri. Well before that, the vernacular was also used for practical purposes, such as the testimonies in the Placiti Cassinesi, written 960–963. Uniformization and standardization The invention of the printing press brought a tendency towards greater uniformity of standard languages within political boundaries, at the expense of other Romance languages and dialects less favored politically. In France, for instance, the dialect spoken in the region of Paris gradually spread to the entire country, and the Occitan of the south lost ground. Sound changes Consonants Significant sound changes affected the consonants of the Romance languages. Apocope There was a tendency to eliminate final consonants in Vulgar Latin, either by dropping them (apocope) or adding a vowel after them (epenthesis). Many final consonants were rare, occurring only in certain prepositions (e.g. ad "towards", apud "at, near (a