CircularReferenceException error

I need some help, I have this: com.thoughtworks.xstream.core.TreeMarshaller $ CircularReferenceException And I can not find the solution. Here is the snippet of code:

    XStream xstream = new XStream(new JettisonMappedXmlDriver());
    xstream.setMode(XStream.NO_REFERENCES);
    xstream.alias("resultList", ResultList.class);
    xstream.alias("resultRow", ResultRow.class);
    xstream.alias("resultCol", ResultCol.class);

    return xstream.toXML(lista);

Exception occurs in xstream.toXML.

The classes in Java:     public class ResultList implements Serializable {

private List<ResultRow> rows = null;

public List<ResultRow> getRows() {
    if (rows == null) {
        rows = new ArrayList<ResultRow>();
    }
    return rows;
    }

}

public class ResultRow implements Serializable {

private List<ResultCol> columns;

public List<ResultCol> getColumns() {
    if (columns == null) {
        columns = new ArrayList<ResultCol>();
    }
    return columns;
}

public void addColumn(ResultCol col) {
    col.setOrdem(getColumns().size() + 1);
    getColumns().add(col);
}

}

public class ResultCol implements Serializable {

private int ordem = 0;
private T valor;
private String nome;
private String typeName;
private String format;
private String label;
private int type;
private ResultRow row;

public ResultCol(ResultRow row, T valor, String nome, String typeName, int type) {
    this.valor = valor;
    this.nome = nome;
    this.typeName = typeName;
    this.type = type;
    this.format = "";
    this.label = "";
}

public ResultCol(ResultRow row, T valor, String nome, String typeName, int type, String format, String desc) {
    this.valor = valor;
    this.nome = nome;
    this.typeName = typeName;
    this.type = type;
    this.format = format;
    this.label = desc;
}

public T getValor() {
    return valor;
}

public void setValor(T valor) {
    this.valor = valor;
}

public String getNome() {
    return nome;
}

public void setNome(String nome) {
    this.nome = nome;
}

public int getOrdem() {
    return ordem;
}

public void setOrdem(int ordem) {
    int ordemAtual = this.ordem;

    if (ordem < ordemAtual) {

    } else if (ordem > ordemAtual) {

    }

    this.ordem = ordem;
}

public String getTypeName() {
    return typeName;
}

public int getType() {
    return type;
}

public String getFormat() {
    return format;
}

public void setFormat(String format) {
    this.format = format;
}

public String getLabel() {
    return label;
}

public void setLabel(String label) {
    this.label = label;
}

public ResultRow getRow() {
    return row;
}

@Override
public String toString() {
    if (valor == null) {
        return "";
    } else {
        return valor.toString();
    }
}

@Override
public int hashCode() {
    int hash = 3;
    hash = 83 * hash + (this.nome != null ? this.nome.hashCode() : 0);
    return hash;
}

@Override
public boolean equals(Object obj) {
    if (this == obj) {
        return true;
    }
    if (obj == null) {
        return false;
    }
    if (obj instanceof String) {
        return this.nome.equals(obj);
    }
    if (getClass() != obj.getClass()) {
        return false;
    }

    final ResultCol<?> other = (ResultCol<?>) obj;
    if ((this.nome == null) ? (other.nome != null) : !this.nome.equals(other.nome)) {
        return false;
    }
    return true;
}

}

If you are missing something, just ask, I can not find the reason for the error.