Final answer:
Nikolav Vasillev is a fictional or unknown character in relation to the topics mentioned.
Step-by-step explanation:
Nikolav Vasillev was not a famous detective who solved the case, a suspect in the Jack the Ripper case, a prominent victim of the Whitechapel murders or a journalist who covered the killings. There is no historical evidence or credible sources to support these claims.
Based on the information provided, it is likely that Nikolav Vasillev is a fictional or unknown character in relation to the topics mentioned.