Before revision:  Although many approximate/exact algorithms have been developed to solve this  problem on numerous properties, a solution obtained by these algorithms is often unsuitable for real-world applications due to the difficulty of building  mathematical models on real-world problems.
After revision:  Although many approximate/exact algorithms have been developed to solve this problem on numerous properties, a solution obtained by these algorithms is often unsuitable for real-world applications due to the difficulty of building accurate mathematical models on real-world problems.