Citation: K. Helwig et al., GASTRIC ANGIOMYOLIPOMA - A PREVIOUSLY UNDESCRIBED CAUSE OF UPPER GI HEMORRHAGE, The American journal of gastroenterology, 93(6), 1998, pp. 1004-1005
Citation: K. Helwig, A NOTE ON BURNT YELLOW EARTH PIGMENTS - DOCUMENTARY SOURCES AND SCIENTIFIC ANALYSIS( CONSERVATION OF PAINTINGS AND FRESCOES ), Studies in conservation, 42(3), 1997, pp. 181-188
Citation: Mc. Corbeil et K. Helwig, AN OCCURRENCE OF PARAREALGAR AS AN ORIGINAL OR ALTERED ARTISTS PIGMENT, Studies in conservation, 40(2), 1995, pp. 133-138