# VectorDBQAWithSourcesChain

> **Class** in `langchain_classic`

📖 [View in docs](https://reference.langchain.com/python/langchain-classic/chains/qa_with_sources/vector_db/VectorDBQAWithSourcesChain)

Question-answering with sources over a vector database.

## Signature

```python
VectorDBQAWithSourcesChain()
```

## Extends

- `BaseQAWithSourcesChain`

## Properties

- `vectorstore`
- `k`
- `reduce_k_below_max_tokens`
- `max_tokens_limit`
- `search_kwargs`

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[View source on GitHub](https://github.com/langchain-ai/langchain/blob/42f8f79293cfb7589e5bc1d74a8ae4dfd0bf15e3/libs/langchain/langchain_classic/chains/qa_with_sources/vector_db.py#L19)