What is the fine-grained topic of the following text: Social, cultural and linguistic knowledge acquired and transferred across the Atlantic sea route by Italian migrants moving to the USA had created a migration map consisting of a shared corpus of oral and epistolary narratives, shared knowledge about survival strategies, known geographical locations, employment experiences and prospects, and the relative security of established intergenerational family nodes in a place of settlement that had evolved through successive patterns of chain migration. Only return the topic.
Italian migration to the USA and the transfer of socio-cultural and linguistic knowledge.