update SOLUS citation

Author: brownag

R/fetchSOLUS.R

@@ -54,10 +54,11 @@
 #' @return A _SpatRaster_ object containing SOLUS grids for specified extent, depths, variables, and
 #'   product types.
 #'
-#' @references Nauman, T.W., Kienast-Brown, S., White, D.A. Brungard, C.W., Philippe, J., Roecker,
-#'   S.M., Thompson, J.A. Soil Landscapes of the United States (SOLUS): developing predictive soil
-#'   property maps of the conterminous US using hybrid training sets. In Prep for SSSAJ.
-#'
+#' @references Nauman, T. W., Kienast-Brown, S., Roecker, S. M., Brungard, C., White, D., Philippe,
+#'   J., & Thompson, J. A. (2024). Soil landscapes of the United States (SOLUS): developing
+#'   predictive soil property maps of the conterminous United States using hybrid training sets.
+#'   Soil Science Society of America Journal, 88, 2046–2065. \doi{https://doi.org/10.1002/saj2.20769}
+#' 
 #' @author Andrew G. Brown
 #' 
 #' @importFrom stats approxfun splinefun