Update c4frac references

Author: abhaasgoyal

Diff for: regrid_aus_05x05_to_005x005.sh

@@ -665,7 +665,7 @@ att_nm='references'
 var_nm='c4frac'
 mode='o'
 att_type='c'
-att_val='https://doi.org/10.1111/j.1365-2486.2008.01746.x'
+att_val='https://doi.org/10.5194/bg-10-2011-2013 following https://doi.org/10.1007/BF00379569'
 ncatted -h -a "${att_nm}","${var_nm}","${mode}","${att_type}","${att_val}" ${output_file}
 
 bios_soil_vars_regex='^clay$|^sand$|^ssat$|^bch$|^css$|^hyds$|^sfc$|^sucs$|^rhosoil$|^silt$|^swilt$'