Most headers exist as keyword=value pairs (for example /delimeter=comma). Whitespace is not allowed in values; if there are multiple values they are listed comma separated (no space), and if a single value would contain a space it is replaced with underscores (for example /investigators=John_Smith,Mary_Miller). Spaces are only allowed in freeform comment lines which begin with an exclamation point (e.g., ! This is a comment).