(optional) Character string indicating a web page of the Data Repository of the
Brazilian Soil, with options:
"febr"
: FEBR main web page,
"dictionary"
: FEBR data dictionary and vocabulary,
"forum"
: FEBR public forum at Google Groups,
"github"
: febr package source code repository on GitHub,
"index"
: FEBR data set index,
"search"
: data set search web page,
"package"
: febr package on CRAN,
"template"
: FEBR spreadsheet template on Google Sheets,
"units"
: units and conversion factors used in FEBR.