To write the Values element (Vl) in the index.

§1. And here is the indexing code: 

void ValuesElement::render(OUTPUT_STREAM) {
    inter_tree *I = Index::get_tree();
    tree_inventory *inv = Synoptic::inv(I);
    TreeLists::sort(inv->variable_nodes, Synoptic::module_order);
    Index the variables1.1;
    TreeLists::sort(inv->equation_nodes, Synoptic::module_order);
    Index the equations1.2;
}

§1.1. Index the variables1.1 = 

	heading *definition_area, *current_area = NULL;
    HTML_OPEN("p");
    Index::anchor(OUT, I"NAMES");
    int understood_note_given = FALSE;
    for (int i=0; i<TreeLists::len(inv->variable_nodes); i++) {
        inter_package *pack = Inter::Package::defined_by_frame(inv->variable_nodes->list[i].node);
        if (Metadata::read_optional_numeric(pack, I"^indexable")) {
            if (Metadata::read_optional_numeric(pack, I"^understood"))
                Index a K understood variable1.1.1
            else
                Index a regular variable1.1.2;
        }
    }
    HTML_CLOSE("p");

§1.1.1. Index a K understood variable1.1.1 = 

    if (understood_note_given == FALSE) {
        understood_note_given = TRUE;
        WRITE("<i>kind</i> understood - <i>value</i>");
        HTML_TAG("br");
    }

§1.1.2. Index a regular variable1.1.2 = 

	definition_area = Headings::of_wording(nlv->name);
    if (Headings::indexed(definition_area) == FALSE) continue;
    if (definition_area != current_area) {
        wording W = Headings::get_text(definition_area);
        HTML_CLOSE("p");
        HTML_OPEN("p");
        if (Wordings::nonempty(W)) Phrases::Index::index_definition_area(OUT, W, FALSE);
    }
    current_area = definition_area;
*/
    text_stream *name = Metadata::read_optional_textual(pack, I"^name");
    WRITE("%S", name);
    int at = (int) Metadata::read_optional_numeric(pack, I"^at");
    if (at > 0) Index::link(OUT, at);
    text_stream *doc = Metadata::read_optional_textual(pack, I"^documentation");
    if (Str::len(doc) > 0) Index::DocReferences::link(OUT, doc);
    text_stream *contents = Metadata::read_optional_textual(pack, I"^contents");
    WRITE(" - <i>%S</i>", contents);
    HTML_TAG("br");

§1.2. Index the equations1.2 = 

    if (TreeLists::len(inv->equation_nodes) > 0) {
        HTML_OPEN("p"); WRITE("<b>List of Named or Numbered Equations</b> (<i>About equations</i>");
        Index::DocReferences::link(OUT, I"EQUATIONS"); WRITE(")");
        HTML_CLOSE("p");
        HTML_OPEN("p");
        int N = 0;
        for (int i=0; i<TreeLists::len(inv->equation_nodes); i++) {
            inter_package *pack = Inter::Package::defined_by_frame(inv->equation_nodes->list[i].node);
            int at = (int) Metadata::read_optional_numeric(pack, I"^at");
            if (at > 0) {
    			WRITE("%+W", Wordings::up_to(Node::get_text(eqn->equation_created_at), mw));
                Index::link(OUT, at);
    			WRITE(" (%+W)", eqn->equation_text);
                HTML_TAG("br");
                N++;
            }
        }
        if (N == 0) WRITE("<i>None</i>.\n");
        HTML_CLOSE("p");
    }