Нашёл 2 млн ответов for 'fuctions of external'.
https://docs.snowflake.com/en/sql-reference/external-functions-introduction.html
https://docs.snowflake.com/en/sql-reference/external-functions-implementation.html
https://docs.snowflake.com/en/sql-reference/external-functions-general.html
https://docs.mql4.com/basis/function/extfunctions
https://docs.microsoft.com/en-us/dotnet/fsharp/language-reference/functions/external-functions
https://docs.microsoft.com/hi-in/dotnet/fsharp/language-reference/functions/external-functions
https://docs.moodle.org/dev/External_functions_API
http://media.datadirect.com/download/docs/ddxquery/allddxq/reference/advancedfeatures9.html
https://obliquity.com/computer/fortran/procedure.html
https://www.orcina.com/webhelp/OrcaFlex/Content/html/Externalfunctions.htm