In the back of most cookery books there is an index for the recipes included; however, I’m not sure there are many indices with a preface! Philip Harben has a preface to his index in his Cooking Quickly, published in 1946:
HOW TO USE THIS INDEX
This is no ordinary index. In it you will find not only every dish and subject mentioned in this book, but also a cross-reference to every leading ingredient.
For instance, if your kitchen foraging reveals a useful quantity of tomatoes or a sufficiency of cheese, then the index will lead you to Bolognese Sauce for Spaghetti or Welsh Rarebit. The index will show you at a glance the possibilities of bacon, the uses of cooked meat, and what can be done with left-over cold potatoes.
To simplify the journey from the index to the page, most of the indexed words are printed in the text in SMALL CAPITALS.