Fernando Galván, José Francisco2023-06-202023-06-202002Fernando, J. Positive semidefinite germs in real analytic surfaces. Math Ann 322, 49–67 (2002). https://doi.org/10.1007/s0020801002640025-583110.1007/s002080100264https://hdl.handle.net/20.500.14352/57240We find all real analytic surface germs in R3 on which every positive semidefinite function germ is a sum of squares (in fact, of two squares) of analytic function germs.engjournal articlehttps://doi.org/10.1007/s002080100264http://www.springerlink.com/restricted access517.98Sums of squaresAnalytic ringsAnalytic function germsPositive semidefinite functionsBrieskorn singularityAnálisis funcional y teoría de operadores