To find the citation for a thing, e.g. function, type, or module. use the cite(thing) command.

To declare a citation for a function attach it as a trait on the type of the function. This is done

function thing()
#...
end

Citations.cite(::typeof(thing) = "2001, Jane Doe, Considerations of a Thing"

Or you can use the helper macro @declare_citation:

@declare_citation thing,  "2001, Jane Doe, Considerations of a Thing"

To declare a citation for a module, declare a cite trait for the modules eval function.

Citation.cite(::typeof(MyModule.eval)) = "2019, Author, Package

Or use the @declare_citation macro, with only one argument.

@declare_citation "2019, Author, Package