This was file recipe.dtd.

<!ELEMENT recipe - - (title,comment?,ingredients,method,source?)>
<!ELEMENT title - - (#PCDATA)>
<!ELEMENT comment - - (#PCDATA)>
<!ELEMENT source - - (#PCDATA)>
<!ELEMENT ingredients - - (ingredient+)>
<!ELEMENT ingredient - o (#PCDATA)>
<!ATTLIST ingredient quant CDATA #REQUIRED
                     units (g|Kg|dl|l|oz|lb|pt|cup|0) #REQUIRED>
<!ELEMENT method - - (para|list)>
<!ELEMENT para - - (#PCDATA)>
<!ELEMENT list - - (item+)>
<!ELEMENT item - o (#PCDATA)>
<!ENTITY deg CDATA "&#176;">
<!ENTITY frac12 CDATA "&#189;">