RStudio will not write a .bbl file when compiling .Rnw file with citations in natbib - Stack Overflow
Use bib files in Latex to generate bbl format files in batches - Programmer Sought
When writing latex under WinEdt and using bibTex references, I encountered Citation xxx on page xxx undefined on input l or annot find example.bcf - Programmer Sought
Use bib files in Latex to generate bbl format files in batches - Programmer Sought
BibTeX - Wikipedia
How-to series: Generate BibTeX files for your collections for use in LaTeX [part 3 of 12] – Mendeley Blog