Set the different path in yaml options using rmarkdown

My Rmd files and bib files in different path. Their parent directory are the folders a and b. And the two folders are in the folder c.

When I want add bibliopraphy in the Rmd files, my yaml option block looks like,

title: "R Notebook"
output: html_notebook
bibliography: ../b/add.bib

But the error message shows my path is wrong. Anyone know the right way to wirte the path?

Here is my session info.

#> R version 3.4.4 (2018-03-15)
#> Platform: x86_64-w64-mingw32/x64 (64-bit)
#> Running under: Windows 7 x64 (build 7601) Service Pack 1
#> Matrix products: default
#> locale:
#> [1] LC_COLLATE=Chinese (Simplified)_People's Republic of China.936 
#> [2] LC_CTYPE=Chinese (Simplified)_People's Republic of China.936   
#> [3] LC_MONETARY=Chinese (Simplified)_People's Republic of China.936
#> [4] LC_NUMERIC=C                                                   
#> [5] LC_TIME=Chinese (Simplified)_People's Republic of China.936    
#> attached base packages:
#> [1] stats     graphics  grDevices utils     datasets  methods   base     
#> loaded via a namespace (and not attached):
#>  [1] compiler_3.4.4  backports_1.1.2 magrittr_1.5    rprojroot_1.3-2
#>  [5] formatR_1.5     tools_3.4.4     htmltools_0.3.6 yaml_2.1.19    
#>  [9] Rcpp_0.12.17    stringi_1.1.7   rmarkdown_1.9   knitr_1.20     
#> [13] stringr_1.3.0   digest_0.6.15   evaluate_0.10.1

Can you post the exact error message so that we know what it is really about ?

I suspect it come from here because you use relative path to a parent folder and I am not sure it is possible. It a guess based on past issue that seems related to me, but I can't find in the doc where it is written that parent directory are not possible.

I know that rmarkdown::find_external_ressources do not work with parent directory.

In all cases, only resources that exist on disk and are contained in the document's directory (or a child thereof) are returned.

Is it working if you put the .bib in the same folder as the document ?