Please answer a question about the following article about Dutch language:

Attestations of Old Dutch sentences are extremely rare. The oldest one first recorded has been found in the Salic law. From this Frankish document written around 510 the oldest sentence has been identified as Dutch: Maltho thi afrio lito (I say to you, I free you, serf) used to free a serf. Another old fragment of Dutch is Visc flot aftar themo uuatare (A fish was swimming in the water). The oldest conserved larger Dutch text is the Utrecht baptismal vow (776-800) starting with Forsachistu diobolae [...] ec forsacho diabolae (Do you forsake the devil? [...] I forsake the devil). Probably the most famous sentence Hebban olla vogala nestas hagunnan, hinase hic enda tu, wat unbidan we nu (All birds have started making nests, except me and you, what are we waiting for), is dated around the year 1100, written by a Flemish monk in a convent in Rochester, England.

Are written records of Old Dutch rare or common?
rare