secondary source
Used in academic research and computing contexts to refer to documents or data derived from primary sources.
When writing a paper, you need to consult not only primary sources but also secondary sources.
一次資料 refers to a primary source (original material), while 二次資料 is a secondary source that analyzes or interprets primary sources.
Compound of 二次 (にじ, 'secondary') and 資料 (しりょう, 'materials, data'). The term is a direct conceptual borrowing from English 'secondary source'.