On King Type Modification of $(p,q)$ Baskakov Operators which preserves   $x^2$
  In the present paper, we construct and investigate a variant of modified $(p,q)$-Baskakov operators, which reproduce the test function $x^2$. The order of approximation of the operators via K-functional and second order, usual modulus of continuity, weighted approximation properties are disscussed. In the end some graphical results, comparison with $(p,q)$-Baskakov operators is explained. 
Shikha Pandey, Vishnu Narayan Mishra, L N Mishra
math.CA