In his work "De Administrando Imperio", Constantine Porphyrogenitus mentions the White Croatia (originally Βελοχρωβάτοι i Χρωβάτοι) as the place from which, in the 7th century, part of Croatian tribes started their journey to Balkans (more specific, today's Croatia) after they were invited there by the Byzantine Empire (emperor Flavius Heraclius Augustus) to protect its borders. This migration was described by Adam Naruszewicz in his work "The History of Polish Nation": "The Chrobats were known even in the 9th century under Constantine Porphyrogennetos rule, who describes them in his work De Administrando Imperio in these words: The Chrobat lived in that times (meaning, times of emperror Heraclius) close to Babigorea where Belo-Chobat family is now, while others, those who went to Dalmatia living close to France, called Belo-Chrobat, belo meaning white, as they had their own Prince. They pay hommage to Otto the Great, the ruler of Franks also being Saxon. Being pagans they ally with Turks. Those Chrobats who in Dalatia reside, derive from the non baptized ones, ones allied Turks living near Franks and with Serbians bordering." Then he also states: "[...] the great Chrobatia which as the white is called, till this very day baptised is not, same as their neighbours Serbians. Cavalry and infantry has it as much as Christian Chrobatia, all for frequent Franks' invasions."
According to Nestor the Chronicler, White Croats where progenitors of Lendians. In his work from 1113 A.D. called "The Primary Chronicle" Nestor describes how in the early middle ages White Croats, Serbians and Karantans (most likely part of the tribes) were forced to leave their lands due to Italian invasion. After that they settled along Vistula river, calling themselves Lendians, and later dividing into Polans, Veleti, Masovier and Pomeranians. "After many years had passed, Slavic people settled on the Danube, where Hungary and Bulgaria are now. From those Slavic tribes they spread to many lands, calling themselves with many names which were from grounds they stayed on. And so, leaving on the Morava river, they called themselves Moravians, and anothers as Czech. Yet another Slavic people were White Croatians, and Serbians, and Korantans. Those, when oppressed by Italians who invaded that grounds, embarked towards Vistula and stayed there calling themselves Lendians, and later Polans, Veleti, Masovier and Pomeranians." Other authors from those tiems are not calling Croatians as "White". The Bavarian Geographer does not mention them either (same as Polans)(845 A.D.).
North of the Great Moravia is where Alfred the Great states as Croatian lands (890 A.D.). In his "Geography of the Europe" relaying on Orosius, Alfred the Great says : "To the north-east of the Moravians are the Dalamensae; east of the Dalamensians are the Horithi (White Croats), and north of the Dalamensians are the Servians; to the west also are the Silesians. To the north of the Horiti is Mazovia, and north of Mazovia are the Sarmatians, quite to the Riphaean mountains."
Nestor in his "The Primary Chronicle" mentions Croatians (but not calling them "White") as one of the russniak tribes. In 907 A.D. they allied with Oleg of Novgorod and took part in his military expedition against Bizantium. It is also mentioned there that Vladimir I of Kiev fought Croatians in 992 A.D. In addition, the name "chrowati et altera chrowati" is mentioned in so called Prague document from 1086 A.D. as the frontier of the Prague diocese. That statement was used as the propaganda to justify the annexation of Galicia during the partions of Poland.
Cosmas of Prague in his Chronica Boëmorum describes grounds of Prague diocese in these words: "[...] The border of which towards the West are as following: Tuhośt, which stretch from the middle of Chamb river, Siedliczanie, Leczanie, Dieczanie, Litomierzyć, Lemuzi, until the forest which the Chech border is. Next, the northern borders, are: Pszowianie, Croatians and other Croatians, Ślęzanie, Trzebowianie, Bobrzanie, Dziadoszanie, up to the middle of the forest which the Milczanie are surrounded. From there to the East the rivers of Styr and Bug are its boarders, together with Krakow and its land name of which is Wag and all the lands belonging to the mentioner Krakow. Then it stretches along Hungarian marches up to the mountains which are called Tatras. Next, in the part which stretches towards the South, when joined with Moravian lands, it reaches Wag river and then Mure, being the name of the forest and the river bordering Bavaria." In the 12th Century, Presbyter Diocleatis in his "History of Slavic Kingdom" uses the term White Croatia with reference to the North Dalmatia.
Wincenty Kadłubek in his "Polish Chronicle" (book II, chapter 12), describes the deeds of Bolesław I the Brave who "conquered Selencja, Pomerania, Prussia, Rus, Moravia, Czech, which he has left his successors as fiefdoms. The city of Prague was called the second capital of his kingdom. He ruled many tribes of Huns Hungarians Croatians and Mards."