Changes
Added missing function argument.
function doi(frame, id)
local text = hideinprint(frame, "[[Digital object identifier|doi]]:[http://dx.doi.org/{{urlencode:" .. id .. "}} " .. tag(frame, {name="nowiki",contents=id,params={}}) .. "]")
if ( string.sub(id,1,3) ~= "10." ) then
text = text .. "[[Category:Pages with DOI errors]]"