I prefer the follow books and journals:

Hermann R. Sweet 'The Genus Phalaenopsis'

Orchid Digest, Orchid of the World Volume 1, 1980

Buch: Sweet, Genus Phalaenopsis

Olaf Gruss / Manfred Wolff 'Phalaenopsis'

Publisher: Verlag Eugen Ulmer, Stuttgart  1995

Buch: Gruss/Wolff, Phalaenopsis

Eric A. Christenson 'Phalaenopsis - A Monograph'

Timber Press, Inc., Portland, Oregon, 2001

Buch: Christenson, Phalaenopsis - A Monograph

Chiba Masaaki 'Phalaenopsis Species'

Chiba Masaaki Phalaenopsis Species Publishing Society, Sakado, Saitama (Japan), 2002

Buch: Christenson, Phalaenopsis - A Monograph

Orchid Digest Vol. 66 (4), Phalaenopsis

The Orchid Digest Corporation, 2002

Journal: Orchid Digest, Phalaenopsis