Title : Proofs using PhoX and new_command Abstract : We'll present a proof of a topological property written in a natural language (english here). This proof will then be translated into new_command, commands in the proof assistant PhoX which have a syntax close to natural language and a restricted vocabulary. We'll present some difficulties that can be found while translating natural language to new_command. The new_command given to the proof assistant implies a formula that must be proved in order to obtain a new state into the proof. We will so study some formulas that the automatic prover of PhoX may have to prove.