on Sparse Languages L such that LL = Sigma. - Per Enflo; Andrew Granville; Jeffrey O. Shallit; Sheng Yu 001 (Discret. Appl. Math., 1994)

Stable basis families and complexity lower bounds - Per Enflo; Meera Sitharam (Electron. Colloquium Comput. Complex., 1996)

Sufficiency and duality for multiobjective control problems under generalized (B, rho)-type I functions. - Khadija Khazafi; Norma G. Rueda; Per Enflo (J. Glob. Optim., 2010)