Keiki Yokoo; Masanori Shiratori; Kimiyuki Ikeda; Yasuaki Umeda; Mitsuo Otsuka; Hirotaka Nishikiori; Hirofumi Chiba; Hiroyuki Koba; Hiroki Takahashi. Significance of Combined Emphysema in Idiopathic Pulmonary Fibrosis and Serum Surfactant Protein-D As a Prognostic Factor. Pulmonary Research and Respiratory Medicine – Open Journal 2017, 4, 24-32.