I have been doing some research in Gauss codes and have been reading Kauffman's paper [Virtual Knot Theory](https://arxiv.org/abs/math/9811028). In section 3.3, Theorem 2, he states that 


*If $K$ is a virtual knot whose underlying Gauss code is planar and whose sign sequence is standard, then $K$ is equivalent to a classical knot.*


He then goes on to say that "The fundamental problem in Gauss codes is to give an algorithm for determining whether a given code can be realized by a planar shadow."


One problem I have is that I can't figure out what exactly the word *standard* means in the theorem - he says he will define it later and never does. And does he actually solve this "fundamental problem" in the rest of the section 3.3. If anyone knows a technical definition of standard, I would be very appreciative. 


The point is to figure out if the the follow question is open:


**Given a Gauss Code, is there an (explicit) algorithm for detecting if it can be realized as a classical knot?**


So if you know that it is or is not open, I would love to know too. In the case that it is known, a reference would be wonderful too. Thanks.



Gauss Codes that produce classical knots as opposed to virtual knots
A simple and efficient characterization of the Gauss codes of classical knots 
is given in de Fraysseix and de Mendez, On a characterization of Gauss codes. 
Discrete Comput. Geom. 22 (1999), no. 2, 287–295. MR1698548 (2000i:05056b)


