How to look up historical stock prices?
![Image](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhFj7ta3eltHslu4yoNNd_eONRszY61i_fevFzD6seeHH7pRIKVoCfNTIV0GMu8PYoXJDqgqRDla5K-1bg5emb124pkMFrOVZlotjdr2szv3FgCdmZqPe8EOwCi6XwaV0_bXIZxWfA4S0w2/s1600/yahoo_finance_search_stock.png)
Looking up historical stock data may be useful for analysis eg.: you may observe in data how news affect stock price. You may also look up historical data to settle accounting debates. This is a quite tough problem since data sources are not always reliable.