The block below was distilled from source material for the topic "{topic}", but its wording drifted from the material: the title may use terms that never literally appear in the sources (translated, expanded, or spelling-corrected), and the description may be missing.

BLOCK:
Title: {title}
Description: {description}

MATERIAL EXCERPTS:
{excerpts}

Tasks:
- "title": If the title's terms do not literally appear in the excerpts, rewrite it using ONLY surface forms (exact spellings, even unusual ones) that appear in the excerpts — same meaning, same concreteness, max 8 words. If the title already matches the material wording, repeat it unchanged. Never broaden to a textbook term the excerpts don't use; NO catalog/reference brackets ("(Satz 6.33)", "(Kap. 4)"). A source numbering ("Satz 7.13", "Definition 6.19") is NOT a valid title even when it appears literally in the excerpts — use the concept/result name from the excerpts; the numbering may go into the description.
- "description": If the description is "(leer)", write ONE precise sentence grounded in the excerpts — no invented facts. Otherwise repeat it unchanged.

Reply with ONLY the JSON — no code fences, no other text.

Format:
{{"title": "…", "description": "…"}}