Drawings submitted in international applications (PCT) are required to comply with PCT Rule 11.13, which does not permit color drawings. Furthermore, there is no provision for photographs within the PCT Regulations. Nevertheless, black and white photographs will be accepted where it is impossible to represent in a drawing what is to be shown (e.g., crystalline structures). Color photographs are not permitted in international applications (PCT) (see also section K1).The United States Receiving Office may invite the applicant to correct any defects in the drawings or photographs if they do not comply with PCT Rule 11.13.