I won't try to translate it for you (I actually suprised myself as I could read most of it!) but fortunately the abstract is in English.
SSRN-102 Errors in Company Valuations (102 Errores en Valoraciones de Empresas) by Pablo FernÃ¡ndez:
"This paper contains a collection and classification of 96 errors seen in company valuations performed by financial analysts, investment banks and financial consultants. The author had access to most of the valuations referred to in this paper in his capacity as a consultant in company acquisitions, sales, mergers, and arbitrage processes.
We classify the errors in six main categories: 1) Errors in the discount rate calculation and concerning the riskiness of the company; 2) Errors when calculating or forecasting the expected cash flows; 3) Errors in the calculation of the residual value; 4) Inconsistencies and conceptual errors; 5) Errors when interpreting the valuation; and 6) Organizational errors"