L-Carnitine Study 2016; Comparison of the effect of a combination of eight micronutrients versus a standard mono preparation on sperm parameters; Lipovac et al.; inclusion criteria: 20-60 years of age; ≥ 1 year of subfertility and at least one recent pathological semen analysis result (≤ 3 months); exclusion criteria: aspermia, varicocele, azoospermia, urogenital infections.