The content entity MUST be the second entity in the MIME multipart/related message. The control entity MUST be the first entity in the MIME multipart/related message. The MIME type "multipart/form-data" is used to express values submitted through a form. A multipart/encrypted message has two parts. "Multipart/report" is a message type that contains data formatted for a mail server to read. A MIME type was also assigned to AppleDouble, multipart/appledouble. Multipart/digest is a simple way to send multiple text messages. The multipart/byterange is used to represent noncontiguous byte ranges of a single message. A multipart/signed message is used to attach a digital signature to a message. Applications must treat unrecognized subtypes as "multipart/mixed". If an impact printer is used multiple simultaneous copies can be printed on multipart forms. Safe-Tcl can be included in e-mail when the "application/safe-tcl" and "multipart/enabled-mail" are supported. This makes life easier for users of clients that do not understand multipart messages. Burton arranged the middle section, which features its moody bass line and multipart guitar harmonies. On several occasions, multipart story arcs were created to serve as backgrounds for national contests.