CORE LABORATORIES N.V.  Schedule II - Valuation and Qualifying Account (1)  Comprised primarily of differences due to changes in exchange rate. (In thousands) Balance at  Beginning of  Period Additions  Charged to/ Recovered  from Expense Write-offs Other (1) Balance at  End of Period Year ended December 31, 2013 Reserve for doubtful accounts $ 3,516 $ (236) $ (476) $ 68 $ 2,872 Year ended December 31, 2012 Reserve for doubtful accounts $ 3,762 $ 508 $ (845) $ 91 $ 3,516 Year ended December 31, 2011 Reserve for doubtful accounts $ 3,396 $ 254 $ (281) $ 393 $ 3,762 63