[O] citations not incoprporated from bib file when exporting from .org to pdflatex

[David Abernethy]

I am exporting a file stroke.org using the bibliography file stroke.bib in the same directory

The citations are not being incorporated into the pdf file

An example from stroke.log: LaTeX Warning: Citation `Drummond:2014aa' on page 2 undefined on input line 71.

The header for stroke.org is:

#+LATEX_CLASS: article

#+BIBLIOGRAPHY: stroke vancouver option:-d

My emacs is from MacPorts  GNU Emacs 24.5.1 (x86_64-apple-darwin15.4.0, NS apple-appkit-1404.46)

 of 2016-05-01 on teneleven-slave.macports.org

My .emacs file contains

(setq org-latex-pdf-process '("latexmk -pdflatex='pdflatex -interaction nonstopmode' -pdf -bibtex -f %f"))

Org-mode version 8.3.4 (8.3.4-93-g0d72c3-elpaplus (I updated it as suggested here http://orgmode.org/elpa.html but it made no difference)

I’m using TexLive 2016 with fully up to date packages

Here is the preamble from stroke.tex (no mention of the .bib file)

% Created 2016-06-27 Mon 22:50

\documentclass[12pt]{article}

\usepackage[utf8]{inputenc}

..

\usepackage{wrapfig}

\author{David Abernethy}

\date{\today}

\title{}

\hypersetup{

pdfauthor={David Abernethy},

pdfcreator={Emacs 24.5.1 (Org mode 8.3.4)},..}

\begin{document}

My set up (Latex header in the .org file and .bib file with the .emacs entry) used to work for this file but I have probably updated emacs since.

Can anyone see what is wrong?  help much appreciated

David