Howell, G. C. (1979). Technical evaluation report on the 27th Guidance and Control Panel Symposium on the guidance and control of helicopters and V/STOL aircraft at night and in poor visibility. Neuilly-sur-Seine, France: North Atlantic Treaty Organization, Advisory Group for Aerospace Research & Development.

Howell, G. C. Technical Evaluation Report On the 27th Guidance and Control Panel Symposium On the Guidance and Control of Helicopters and V/STOL Aircraft At Night and in Poor Visibility. Neuilly-sur-Seine, France: North Atlantic Treaty Organization, Advisory Group for Aerospace Research & Development, 1979.

Howell, G. C. Technical Evaluation Report On the 27th Guidance and Control Panel Symposium On the Guidance and Control of Helicopters and V/STOL Aircraft At Night and in Poor Visibility. Neuilly-sur-Seine, France: North Atlantic Treaty Organization, Advisory Group for Aerospace Research & Development, 1979.